diff --git a/.flake8 b/.flake8
index 1b0794e02..ae3e4d470 100644
--- a/.flake8
+++ b/.flake8
@@ -1,4 +1,5 @@
 [flake8]
+max-line-length = 79
 exclude = build
-ignore = E266, W503
+ignore = E203, E266, W503
 per-file-ignores = */api.py:F401
diff --git a/.github/workflows/check-style.yml b/.github/workflows/check-style.yml
new file mode 100644
index 000000000..ec8eb07ca
--- /dev/null
+++ b/.github/workflows/check-style.yml
@@ -0,0 +1,20 @@
+name: Run style checks
+
+on: [pull_request, workflow_dispatch]
+
+jobs:
+  style:
+    runs-on: 'ubuntu-latest'
+
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions/setup-python@v4
+      with:
+        python-version: '3.11'
+        cache: 'pip'
+        cache-dependency-path: '.github/workflows/style-requirements.txt'
+    - run: python -m pip install -r .github/workflows/style-requirements.txt
+    - run: |
+        python -m black --check --diff .
+        python -m isort --check --diff .
+        python -m flake8 .
diff --git a/.github/workflows/style-requirements.txt b/.github/workflows/style-requirements.txt
new file mode 100644
index 000000000..70f461dcc
--- /dev/null
+++ b/.github/workflows/style-requirements.txt
@@ -0,0 +1,4 @@
+black ~= 23.0
+flake8
+flake8-ets
+isort
diff --git a/.github/workflows/test-with-edm.yml b/.github/workflows/test-with-edm.yml
index e6816d450..4f362f7c0 100644
--- a/.github/workflows/test-with-edm.yml
+++ b/.github/workflows/test-with-edm.yml
@@ -45,9 +45,6 @@ jobs:
         run: python -m pip install -r .github/workflows/bootstrap-requirements.txt
       - name: Install test environment
         run: python etstool.py install --runtime=${{ matrix.runtime }} --toolkit=${{ matrix.toolkit }}
-      - name: Flake8
-        run: python etstool.py flake8 --runtime=${{ matrix.runtime }} --toolkit=${{ matrix.toolkit }}
-        if: runner.os == 'Linux' && matrix.toolkit == 'null'
       - name: Run tests (Ubuntu)
         if: matrix.os == 'ubuntu-latest'
         run: xvfb-run -a python etstool.py test --runtime=${{ matrix.runtime }} --toolkit=${{ matrix.toolkit }}
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 049e75e70..6dc1e3474 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -120,7 +120,7 @@
 .. |Message| replace:: :github-demo:`Message <MOTD/acme/motd/message.py>`
 .. |messages.py| replace:: :github-demo:`message.py <MOTD/acme/motd/software_quotes/messages.py>`
 .. |Message of the Day| replace:: :github-demo:`Message of the Day <MOTD>`
-"""   # noqa: E501
+"""  # noqa: E501
 
 # Options for HTML output
 # -----------------------
@@ -234,7 +234,8 @@
 # -- Options for extlinks extension -------------------------------------------
 
 extlinks = {
-    'github-demo': (
-        f'https://github.com/enthought/envisage/tree/{version}/envisage/examples/demo/%s',   # noqa: E501
-        '')
+    "github-demo": (
+        f"https://github.com/enthought/envisage/tree/{version}/envisage/examples/demo/%s",  # noqa: E501
+        "",
+    )
 }
diff --git a/envisage/api.py b/envisage/api.py
index 8a498a614..bce27b546 100644
--- a/envisage/api.py
+++ b/envisage/api.py
@@ -66,6 +66,18 @@
 
 """
 
+from .application import Application
+from .core_plugin import CorePlugin
+from .egg_plugin_manager import EggPluginManager
+from .extension_point import ExtensionPoint
+from .extension_point_binding import (
+    bind_extension_point,
+    ExtensionPointBinding,
+    unbind_extension_point,
+)
+from .extension_point_changed_event import ExtensionPointChangedEvent
+from .extension_provider import ExtensionProvider
+from .extension_registry import ExtensionRegistry
 from .i_application import IApplication
 from .i_extension_point import IExtensionPoint
 from .i_extension_point_user import IExtensionPointUser
@@ -76,19 +88,6 @@
 from .i_plugin_activator import IPluginActivator
 from .i_plugin_manager import IPluginManager
 from .i_service_registry import IServiceRegistry
-
-from .application import Application
-from .core_plugin import CorePlugin
-from .egg_plugin_manager import EggPluginManager
-from .extension_registry import ExtensionRegistry
-from .extension_point import ExtensionPoint
-from .extension_point_binding import (
-    ExtensionPointBinding,
-    bind_extension_point,
-    unbind_extension_point,
-)
-from .extension_provider import ExtensionProvider
-from .extension_point_changed_event import ExtensionPointChangedEvent
 from .ids import (
     BINDINGS,
     COMMANDS,
@@ -96,8 +95,8 @@
     PREFERENCES_CATEGORIES,
     PREFERENCES_PANES,
     SERVICE_OFFERS,
+    TASK_EXTENSIONS,
     TASKS,
-    TASK_EXTENSIONS
 )
 from .import_manager import ImportManager
 from .plugin import Plugin
diff --git a/envisage/application.py b/envisage/application.py
index 8cafc246a..66f025f35 100644
--- a/envisage/application.py
+++ b/envisage/application.py
@@ -15,31 +15,40 @@
 import os
 
 # Enthought library imports.
-from apptools.preferences.api import IPreferences, ScopedPreferences
-from apptools.preferences.api import set_default_preferences
+from apptools.preferences.api import (
+    IPreferences,
+    ScopedPreferences,
+    set_default_preferences,
+)
 from traits.api import (
-    Delegate, Event, HasTraits, Instance, observe, provides, Str, VetoableEvent
+    Delegate,
+    Event,
+    HasTraits,
+    Instance,
+    observe,
+    provides,
+    Str,
+    VetoableEvent,
 )
 from traits.etsconfig.api import ETSConfig
 
+from .application_event import ApplicationEvent
+
 # Local imports.
 from .i_application import IApplication
 from .i_extension_registry import IExtensionRegistry
 from .i_import_manager import IImportManager
 from .i_plugin_manager import IPluginManager
 from .i_service_registry import IServiceRegistry
-
-from .application_event import ApplicationEvent
 from .import_manager import ImportManager
 
-
 # Logging.
 logger = logging.getLogger(__name__)
 
 
 @provides(IApplication)
 class Application(HasTraits):
-    """ An extensible, pluggable, application.
+    """An extensible, pluggable, application.
 
     This class handles the common case for non-GUI applications, and it is
     intended to be subclassed to change start/stop behaviour etc.
@@ -113,7 +122,7 @@ class Application(HasTraits):
     ###########################################################################
 
     def __init__(self, plugins=None, **traits):
-        """ Constructor.
+        """Constructor.
 
         We allow the caller to specify an initial list of plugins, but the list
         itself is not part of the public API. To add and remove plugins after
@@ -154,27 +163,28 @@ def __init__(self, plugins=None, **traits):
     #### Trait initializers ###################################################
 
     def _home_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return ETSConfig.application_home
 
     def _user_data_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return ETSConfig.user_data
 
     def _preferences_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return ScopedPreferences(
             application_preferences_filename=os.path.join(
-                self.home, 'preferences.ini')
+                self.home, "preferences.ini"
+            )
         )
 
     #### Methods ##############################################################
 
     def run(self):
-        """ Run the application. """
+        """Run the application."""
 
         if self.start():
             self.stop()
@@ -184,52 +194,48 @@ def run(self):
     ###########################################################################
 
     def add_extension_point_listener(self, listener, extension_point_id=None):
-        """ Add a listener for extensions being added/removed. """
+        """Add a listener for extensions being added/removed."""
 
         self.extension_registry.add_extension_point_listener(
             listener, extension_point_id
         )
 
     def add_extension_point(self, extension_point):
-        """ Add an extension point. """
+        """Add an extension point."""
 
         self.extension_registry.add_extension_point(extension_point)
 
     def get_extensions(self, extension_point_id):
-        """ Return a list containing all contributions to an extension point.
-
-        """
+        """Return a list containing all contributions to an extension point."""
 
         return self.extension_registry.get_extensions(extension_point_id)
 
     def get_extension_point(self, extension_point_id):
-        """ Return the extension point with the specified Id. """
+        """Return the extension point with the specified Id."""
 
         return self.extension_registry.get_extension_point(extension_point_id)
 
     def get_extension_points(self):
-        """ Return all extension points that have been added to the registry.
-
-        """
+        """Return all extension points that have been added to the registry."""
 
         return self.extension_registry.get_extension_points()
 
     def remove_extension_point_listener(
         self, listener, extension_point_id=None
     ):
-        """ Remove a listener for extensions being added/removed. """
+        """Remove a listener for extensions being added/removed."""
 
         self.extension_registry.remove_extension_point_listener(
             listener, extension_point_id
         )
 
     def remove_extension_point(self, extension_point_id):
-        """ Remove an extension point. """
+        """Remove an extension point."""
 
         self.extension_registry.remove_extension_point(extension_point_id)
 
     def set_extensions(self, extension_point_id, extensions):
-        """ Set the extensions contributed to an extension point. """
+        """Set the extensions contributed to an extension point."""
 
         self.extension_registry.set_extensions(extension_point_id, extensions)
 
@@ -238,7 +244,7 @@ def set_extensions(self, extension_point_id, extensions):
     ###########################################################################
 
     def import_symbol(self, symbol_path):
-        """ Import the symbol defined by the specified symbol path. """
+        """Import the symbol defined by the specified symbol path."""
 
         return self._import_manager.import_symbol(symbol_path)
 
@@ -247,27 +253,27 @@ def import_symbol(self, symbol_path):
     ###########################################################################
 
     def __iter__(self):
-        """ Return an iterator over the manager's plugins. """
+        """Return an iterator over the manager's plugins."""
 
         return iter(self.plugin_manager)
 
     def add_plugin(self, plugin):
-        """ Add a plugin to the manager. """
+        """Add a plugin to the manager."""
 
         self.plugin_manager.add_plugin(plugin)
 
     def get_plugin(self, plugin_id):
-        """ Return the plugin with the specified Id. """
+        """Return the plugin with the specified Id."""
 
         return self.plugin_manager.get_plugin(plugin_id)
 
     def remove_plugin(self, plugin):
-        """ Remove a plugin from the manager. """
+        """Remove a plugin from the manager."""
 
         self.plugin_manager.remove_plugin(plugin)
 
     def start(self):
-        """ Start the plugin manager.
+        """Start the plugin manager.
 
         Returns True unless the start was vetoed.
 
@@ -296,12 +302,12 @@ def start(self):
         return not event.veto
 
     def start_plugin(self, plugin=None, plugin_id=None):
-        """ Start the specified plugin. """
+        """Start the specified plugin."""
 
         return self.plugin_manager.start_plugin(plugin, plugin_id)
 
     def stop(self):
-        """ Stop the plugin manager.
+        """Stop the plugin manager.
 
         Returns True unless the stop was vetoed.
 
@@ -333,7 +339,7 @@ def stop(self):
         return not event.veto
 
     def stop_plugin(self, plugin=None, plugin_id=None):
-        """ Stop the specified plugin. """
+        """Stop the specified plugin."""
 
         return self.plugin_manager.stop_plugin(plugin, plugin_id)
 
@@ -344,7 +350,7 @@ def stop_plugin(self, plugin=None, plugin_id=None):
     def get_required_service(
         self, protocol, query="", minimize="", maximize=""
     ):
-        """ Return the service that matches the specified query.
+        """Return the service that matches the specified query.
 
         Raise a 'NoSuchServiceError' exception if no such service exists.
 
@@ -357,7 +363,7 @@ def get_required_service(
         return service
 
     def get_service(self, protocol, query="", minimize="", maximize=""):
-        """ Return at most one service that matches the specified query. """
+        """Return at most one service that matches the specified query."""
 
         service = self.service_registry.get_service(
             protocol, query, minimize, maximize
@@ -366,17 +372,17 @@ def get_service(self, protocol, query="", minimize="", maximize=""):
         return service
 
     def get_service_from_id(self, service_id):
-        """ Return the service with the specified id. """
+        """Return the service with the specified id."""
 
         return self.service_registry.get_service_from_id(service_id)
 
     def get_service_properties(self, service_id):
-        """ Return the dictionary of properties associated with a service. """
+        """Return the dictionary of properties associated with a service."""
 
         return self.service_registry.get_service_properties(service_id)
 
     def get_services(self, protocol, query="", minimize="", maximize=""):
-        """ Return all services that match the specified query. """
+        """Return all services that match the specified query."""
 
         services = self.service_registry.get_services(
             protocol, query, minimize, maximize
@@ -385,7 +391,7 @@ def get_services(self, protocol, query="", minimize="", maximize=""):
         return services
 
     def register_service(self, protocol, obj, properties=None):
-        """ Register a service. """
+        """Register a service."""
 
         service_id = self.service_registry.register_service(
             protocol, obj, properties
@@ -394,12 +400,12 @@ def register_service(self, protocol, obj, properties=None):
         return service_id
 
     def set_service_properties(self, service_id, properties):
-        """ Set the dictionary of properties associated with a service. """
+        """Set the dictionary of properties associated with a service."""
 
         self.service_registry.set_service_properties(service_id, properties)
 
     def unregister_service(self, service_id):
-        """ Unregister a service. """
+        """Unregister a service."""
 
         self.service_registry.unregister_service(service_id)
 
@@ -410,7 +416,7 @@ def unregister_service(self, service_id):
     #### Trait initializers ###################################################
 
     def _extension_registry_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # Do the import here to emphasize the fact that this is just the
         # default implementation and that the application developer is free
@@ -420,7 +426,7 @@ def _extension_registry_default(self):
         return PluginExtensionRegistry(plugin_manager=self)
 
     def _plugin_manager_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # Do the import here to emphasize the fact that this is just the
         # default implementation and that the application developer is free
@@ -430,7 +436,7 @@ def _plugin_manager_default(self):
         return PluginManager(application=self)
 
     def _service_registry_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # Do the import here to emphasize the fact that this is just the
         # default implementation and that the application developer is free
@@ -464,7 +470,7 @@ def _service_registry_default(self):
 
     @observe("plugin_manager")
     def _update_application(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
         old, new = event.old, event.new
 
         if old is not None:
@@ -476,12 +482,12 @@ def _update_application(self, event):
     #### Methods ##############################################################
 
     def _create_application_event(self):
-        """ Create an application event. """
+        """Create an application event."""
 
         return ApplicationEvent(application=self)
 
     def _initialize_application_home(self):
-        """ Initialize the application directories. """
+        """Initialize the application directories."""
 
         os.makedirs(self.home, mode=0o700, exist_ok=True)
         os.makedirs(self.user_data, exist_ok=True)
diff --git a/envisage/application_event.py b/envisage/application_event.py
index 57b25f70e..97622098c 100644
--- a/envisage/application_event.py
+++ b/envisage/application_event.py
@@ -15,7 +15,7 @@
 
 
 class ApplicationEvent(Vetoable):
-    """ An application event. """
+    """An application event."""
 
     # The application that the event is for.
     application = Instance("envisage.api.IApplication")
diff --git a/envisage/composite_plugin_manager.py b/envisage/composite_plugin_manager.py
index c96fc1e82..68d150612 100644
--- a/envisage/composite_plugin_manager.py
+++ b/envisage/composite_plugin_manager.py
@@ -15,7 +15,13 @@
 
 # Enthought library imports.
 from traits.api import (
-    Event, HasTraits, Instance, List, observe, on_trait_change, provides,
+    Event,
+    HasTraits,
+    Instance,
+    List,
+    observe,
+    on_trait_change,
+    provides,
 )
 
 # Local imports.
@@ -25,14 +31,13 @@
 from .plugin_event import PluginEvent
 from .plugin_manager import PluginManager
 
-
 # Logging.
 logger = logging.getLogger(__name__)
 
 
 @provides(IPluginManager)
 class CompositePluginManager(HasTraits):
-    """ A plugin manager composed of other plugin managers!
+    """A plugin manager composed of other plugin managers!
 
     e.g::
 
@@ -106,7 +111,7 @@ def __plugins_default(self):
     #### 'object' protocol ####################################################
 
     def __iter__(self):
-        """ Return an iterator over the manager's plugins. """
+        """Return an iterator over the manager's plugins."""
 
         plugins = []
         for plugin_manager in self.plugin_managers:
@@ -118,12 +123,12 @@ def __iter__(self):
     #### 'IPluginManager' protocol ############################################
 
     def add_plugin(self, plugin):
-        """ Add a plugin to the manager. """
+        """Add a plugin to the manager."""
 
         raise NotImplementedError
 
     def get_plugin(self, plugin_id):
-        """ Return the plugin with the specified Id. """
+        """Return the plugin with the specified Id."""
 
         for plugin in self:
             if plugin_id == plugin.id:
@@ -135,18 +140,18 @@ def get_plugin(self, plugin_id):
         return plugin
 
     def remove_plugin(self, plugin):
-        """ Remove a plugin from the manager. """
+        """Remove a plugin from the manager."""
 
         raise NotImplementedError
 
     def start(self):
-        """ Start the plugin manager. """
+        """Start the plugin manager."""
 
         for plugin in self:
             self.start_plugin(plugin)
 
     def start_plugin(self, plugin=None, plugin_id=None):
-        """ Start the specified plugin. """
+        """Start the specified plugin."""
 
         plugin = plugin or self.get_plugin(plugin_id)
         if plugin is not None:
@@ -158,7 +163,7 @@ def start_plugin(self, plugin=None, plugin_id=None):
             raise ValueError("no such plugin %s" % plugin_id)
 
     def stop(self):
-        """ Stop the plugin manager. """
+        """Stop the plugin manager."""
 
         # We stop the plugins in the reverse order that they were started.
         stop_order = list(iter(self))
@@ -168,7 +173,7 @@ def stop(self):
             self.stop_plugin(plugin)
 
     def stop_plugin(self, plugin=None, plugin_id=None):
-        """ Stop the specified plugin. """
+        """Stop the specified plugin."""
 
         plugin = plugin or self.get_plugin(plugin_id)
         if plugin is not None:
diff --git a/envisage/core_plugin.py b/envisage/core_plugin.py
index 28f16e0e7..24d3a4b49 100644
--- a/envisage/core_plugin.py
+++ b/envisage/core_plugin.py
@@ -11,15 +11,16 @@
 
 from contextlib import closing
 
+from traits.api import List, on_trait_change, Str
+
 # Enthought library imports.
 from envisage.extension_point import ExtensionPoint
 from envisage.plugin import Plugin
 from envisage.service_offer import ServiceOffer
-from traits.api import List, on_trait_change, Str
 
 
 class CorePlugin(Plugin):
-    """ The Envisage core plugin.
+    """The Envisage core plugin.
 
     The core plugin offers facilities that are generally useful when building
     extensible applications such as adapters and hooks etc. It does
@@ -82,7 +83,7 @@ class CorePlugin(Plugin):
 
     @on_trait_change("preferences_items")
     def _update_preferences(self, event):
-        """ React to new preferencess being *added*.
+        """React to new preferencess being *added*.
 
         Note that we don't currently do anything if preferences are *removed*.
 
@@ -115,7 +116,7 @@ def _update_preferences(self, event):
 
     @on_trait_change("service_offers_items")
     def _register_new_services(self, event):
-        """ React to new service offers being *added*.
+        """React to new service offers being *added*.
 
         Note that we don't currently do anything if services are *removed* as
         we have no facility to let users of the service know that the offer
@@ -134,7 +135,7 @@ def _register_new_services(self, event):
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
         # Load all contributed preferences files into the application's root
         # preferences node.
         self._load_preferences(self.preferences)
@@ -151,7 +152,7 @@ def start(self):
     ###########################################################################
 
     def _load_preferences(self, preferences):
-        """ Load all contributed preferences into a preferences node. """
+        """Load all contributed preferences into a preferences node."""
 
         # Enthought library imports.
         from envisage.resource.api import ResourceManager
@@ -170,12 +171,12 @@ def _load_preferences(self, preferences):
                 default.load(f)
 
     def _register_service_offers(self, service_offers):
-        """ Register a list of service offers. """
+        """Register a list of service offers."""
 
         return list(map(self._register_service_offer, service_offers))
 
     def _register_service_offer(self, service_offer):
-        """ Register a service offer. """
+        """Register a service offer."""
 
         service_id = self.application.register_service(
             protocol=service_offer.protocol,
diff --git a/envisage/egg_basket_plugin_manager.py b/envisage/egg_basket_plugin_manager.py
index 8d654a000..4633117f5 100644
--- a/envisage/egg_basket_plugin_manager.py
+++ b/envisage/egg_basket_plugin_manager.py
@@ -22,12 +22,11 @@
 from .egg_utils import add_eggs_on_path, get_entry_points_in_egg_order
 from .plugin_manager import PluginManager
 
-
 logger = logging.getLogger(__name__)
 
 
 class EggBasketPluginManager(PluginManager):
-    """ A plugin manager that finds plugins in eggs on the 'plugin_path'.
+    """A plugin manager that finds plugins in eggs on the 'plugin_path'.
 
     To declare a plugin (or plugins) in your egg use an entry point in your
     'setup.py' file, e.g.
@@ -87,7 +86,7 @@ def _update_path_and_reset_plugins(self, obj, trait_name, removed, added):
     # Protected 'PluginManager' protocol ######################################
 
     def __plugins_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         plugins = self._harvest_plugins_in_eggs(self.application)
 
@@ -98,7 +97,7 @@ def __plugins_default(self):
     #### Private protocol #####################################################
 
     def _create_plugin_from_entry_point(self, ep, application):
-        """ Create a plugin from an entry point. """
+        """Create a plugin from an entry point."""
 
         klass = ep.load()
         plugin = klass(application=application)
@@ -114,7 +113,7 @@ def _create_plugin_from_entry_point(self, ep, application):
         return plugin
 
     def _get_plugin_entry_points(self, working_set):
-        """ Return all plugin entry points in the working set. """
+        """Return all plugin entry points in the working set."""
 
         entry_points = get_entry_points_in_egg_order(
             working_set, self.ENVISAGE_PLUGINS_ENTRY_POINT
@@ -123,7 +122,7 @@ def _get_plugin_entry_points(self, working_set):
         return entry_points
 
     def _harvest_plugins_in_eggs(self, application):
-        """ Harvest plugins found in eggs on the plugin path. """
+        """Harvest plugins found in eggs on the plugin path."""
 
         # We first add the eggs to a local working set so that when we get
         # the plugin entry points we don't pick up any from other eggs
@@ -172,7 +171,7 @@ def _handle_broken_distributions(self, errors):
                 self.on_broken_distribution(dist, exc)
 
     def _update_sys_dot_path(self, removed, added):
-        """ Add/remove the given entries from sys.path. """
+        """Add/remove the given entries from sys.path."""
 
         for dirname in removed:
             if dirname in sys.path:
diff --git a/envisage/egg_plugin_manager.py b/envisage/egg_plugin_manager.py
index 55367c732..4eb046d0b 100644
--- a/envisage/egg_plugin_manager.py
+++ b/envisage/egg_plugin_manager.py
@@ -25,13 +25,12 @@
 from .egg_utils import get_entry_points_in_egg_order
 from .plugin_manager import PluginManager
 
-
 # Logging.
 logger = logging.getLogger(__name__)
 
 
 class EggPluginManager(PluginManager):
-    """ A plugin manager that gets its plugins from Eggs.
+    """A plugin manager that gets its plugins from Eggs.
 
     To declare a plugin (or plugins) in your egg use an entry point in your
     'setup.py' file, e.g.
@@ -89,7 +88,7 @@ def __init__(self, **traits):
     ###########################################################################
 
     def __plugins_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         plugins = []
         for ep in get_entry_points_in_egg_order(
@@ -104,7 +103,7 @@ def __plugins_default(self):
         return plugins
 
     def _working_set_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return pkg_resources.working_set
 
@@ -113,7 +112,7 @@ def _working_set_default(self):
     ###########################################################################
 
     def _create_plugin_from_ep(self, ep):
-        """ Create a plugin from an extension point. """
+        """Create a plugin from an extension point."""
 
         klass = ep.load()
         plugin = klass(application=self.application)
@@ -129,7 +128,7 @@ def _create_plugin_from_ep(self, ep):
         return plugin
 
     def _is_excluded(self, plugin_id):
-        """ Return True if the plugin Id is excluded.
+        """Return True if the plugin Id is excluded.
 
         If no 'exclude' patterns are specified then this method returns False
         for all plugin Ids.
@@ -146,7 +145,7 @@ def _is_excluded(self, plugin_id):
         return False
 
     def _is_included(self, plugin_id):
-        """ Return True if the plugin Id is included.
+        """Return True if the plugin Id is included.
 
         If no 'include' patterns are specified then this method returns True
         for all plugin Ids.
diff --git a/envisage/egg_utils.py b/envisage/egg_utils.py
index 19c8f0742..c44ecded6 100644
--- a/envisage/egg_utils.py
+++ b/envisage/egg_utils.py
@@ -18,7 +18,7 @@
 
 
 def add_eggs_on_path(working_set, path, on_error=None):
-    """ Add all eggs found on the path to a working set. """
+    """Add all eggs found on the path to a working set."""
 
     environment = pkg_resources.Environment(path)
 
@@ -38,7 +38,7 @@ def add_eggs_on_path(working_set, path, on_error=None):
 
 
 def get_entry_points_in_egg_order(working_set, entry_point_name):
-    """ Return entry points in Egg dependency order. """
+    """Return entry points in Egg dependency order."""
 
     # Find all distributions that actually contain contributions to the
     # entry point.
@@ -58,9 +58,7 @@ def get_entry_points_in_egg_order(working_set, entry_point_name):
 
 
 def get_distributions_with_entry_point(working_set, entry_point_name):
-    """ Return all distributions that contribute to an entry point.
-
-    """
+    """Return all distributions that contribute to an entry point."""
 
     distributions = []
     for distribution in working_set:
@@ -71,7 +69,7 @@ def get_distributions_with_entry_point(working_set, entry_point_name):
 
 
 def get_distributions_in_egg_order(working_set, distributions=None):
-    """ Return all distributions in Egg dependency order. """
+    """Return all distributions in Egg dependency order."""
 
     # If no specific list of distributions is specified then use all
     # distributions in the working set.
@@ -91,7 +89,7 @@ def get_distributions_in_egg_order(working_set, distributions=None):
 
 
 def get_requires(working_set, distribution):
-    """ Return all of the other distributions that a distribution requires. """
+    """Return all of the other distributions that a distribution requires."""
 
     requires = []
     for requirement in distribution.requires():
diff --git a/envisage/examples/_demo.py b/envisage/examples/_demo.py
index 2e28f22b4..653c4055b 100644
--- a/envisage/examples/_demo.py
+++ b/envisage/examples/_demo.py
@@ -17,7 +17,7 @@
 
 @contextlib.contextmanager
 def demo_path(path):
-    """ Context manager to temporarily insert the directory containing
+    """Context manager to temporarily insert the directory containing
     the demo script to sys.path such that demo examples can be run using
     local packages.
 
diff --git a/envisage/examples/_etsdemo_info.py b/envisage/examples/_etsdemo_info.py
index 2927db0b5..222dc71e3 100644
--- a/envisage/examples/_etsdemo_info.py
+++ b/envisage/examples/_etsdemo_info.py
@@ -16,7 +16,7 @@
 
 
 def info(request):
-    """ Return a configuration for contributing examples to the
+    """Return a configuration for contributing examples to the
     Demo application.
     Parameters
     ----------
@@ -30,7 +30,5 @@ def info(request):
     return dict(
         version=1,
         name="Envisage Examples",
-        root=(
-            pkg_resources.resource_filename("envisage.examples", "demo")
-        ),
+        root=(pkg_resources.resource_filename("envisage.examples", "demo")),
     )
diff --git a/envisage/examples/demo/GUI_Application/traitsui_gui_app.py b/envisage/examples/demo/GUI_Application/traitsui_gui_app.py
index 5794abec4..35c8fb281 100644
--- a/envisage/examples/demo/GUI_Application/traitsui_gui_app.py
+++ b/envisage/examples/demo/GUI_Application/traitsui_gui_app.py
@@ -10,14 +10,15 @@
 
 """ A simple example of a GUIApplication which wraps a TraitsUI """
 
-from traits.api import HasTraits, Str, Int, Enum, Instance, on_trait_change
+from traits.api import Enum, HasTraits, Instance, Int, on_trait_change, Str
+from traitsui.api import Item, OKCancelButtons, View
+
 from envisage.api import Plugin
 from envisage.ui.gui_application import GUIApplication
-from traitsui.api import View, Item, OKCancelButtons
 
 
 class Person(HasTraits):
-    """ A typical traits model object """
+    """A typical traits model object"""
 
     name = Str("John Doe")
 
@@ -26,12 +27,15 @@ class Person(HasTraits):
     gender = Enum("Male", "Female")
 
     view = View(
-        Item("name"), Item("age"), Item("gender"), buttons=OKCancelButtons,
+        Item("name"),
+        Item("age"),
+        Item("gender"),
+        buttons=OKCancelButtons,
     )
 
 
 class PersonViewPlugin(Plugin):
-    """ The 'Person View' plugin.
+    """The 'Person View' plugin.
 
     This plugin waits for the application to start, and then creates a traits
     UI.
@@ -42,7 +46,7 @@ class PersonViewPlugin(Plugin):
 
     @on_trait_change("application:application_initialized")
     def on_application_start(self):
-        """ Start the UI. """
+        """Start the UI."""
 
         person = Person()
 
@@ -52,7 +56,6 @@ def on_application_start(self):
 
 # Application entry point.
 if __name__ == "__main__":
-
     # Create the application.
     application = GUIApplication(
         id="person_view", plugins=[PersonViewPlugin()]
diff --git a/envisage/examples/demo/Hello_World/hello_world.py b/envisage/examples/demo/Hello_World/hello_world.py
index c9d1ac607..ada39e83a 100644
--- a/envisage/examples/demo/Hello_World/hello_world.py
+++ b/envisage/examples/demo/Hello_World/hello_world.py
@@ -10,13 +10,14 @@
 
 """ The Envisage version of the old chestnut. """
 
+from traits.api import List, Str
+
 # Enthought library imports.
 from envisage.api import Application, ExtensionPoint, Plugin
-from traits.api import List, Str
 
 
 class HelloWorld(Plugin):
-    """ The 'Hello World' plugin.
+    """The 'Hello World' plugin.
 
     This plugin offers a single extension point 'greetings' which is a list of
     greetings, one of which is used to produce the '<greeting> World' message
@@ -35,7 +36,7 @@ class HelloWorld(Plugin):
     # methods are called automatically by Envisage when the application is
     # started and stopped respectively.
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         # Standard library imports.
         #
@@ -47,7 +48,7 @@ def start(self):
 
 
 class Greetings(Plugin):
-    """ A plugin that contributes to the 'greetings' extension point. """
+    """A plugin that contributes to the 'greetings' extension point."""
 
     # This tells us that the plugin contributes the value of this trait to the
     # 'greetings' extension point.
@@ -55,7 +56,7 @@ class Greetings(Plugin):
 
 
 class MoreGreetings(Plugin):
-    """ Another plugin that contributes to the 'greetings' extension point. """
+    """Another plugin that contributes to the 'greetings' extension point."""
 
     # This tells us that the plugin contributes the value of this trait to the
     # 'greetings' extension point.
@@ -64,7 +65,7 @@ class MoreGreetings(Plugin):
     # This shows how you can use a standard trait initializer to populate the
     # list dynamically.
     def _greetings_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         extensions = [
             "The %s application says %s" % (self.application.id, greeting)
@@ -76,7 +77,6 @@ def _greetings_default(self):
 
 # Application entry point.
 if __name__ == "__main__":
-
     # Create the application.
     #
     # An application is simply a collection of plugins. In this case we
diff --git a/envisage/examples/demo/MOTD/acme/motd/api.py b/envisage/examples/demo/MOTD/acme/motd/api.py
index ccad617e5..096637b3a 100644
--- a/envisage/examples/demo/MOTD/acme/motd/api.py
+++ b/envisage/examples/demo/MOTD/acme/motd/api.py
@@ -10,6 +10,5 @@
 
 from acme.motd.i_message import IMessage
 from acme.motd.i_motd import IMOTD
-
 from acme.motd.message import Message
 from acme.motd.motd import MOTD
diff --git a/envisage/examples/demo/MOTD/acme/motd/i_message.py b/envisage/examples/demo/MOTD/acme/motd/i_message.py
index ceb99fa31..35c89dc7a 100644
--- a/envisage/examples/demo/MOTD/acme/motd/i_message.py
+++ b/envisage/examples/demo/MOTD/acme/motd/i_message.py
@@ -16,7 +16,7 @@
 
 
 class IMessage(Interface):
-    """ The interface for 'Message of the Day' messages. """
+    """The interface for 'Message of the Day' messages."""
 
     # The author of the message.
     author = Str
diff --git a/envisage/examples/demo/MOTD/acme/motd/i_motd.py b/envisage/examples/demo/MOTD/acme/motd/i_motd.py
index 5ea082cc1..53655b219 100644
--- a/envisage/examples/demo/MOTD/acme/motd/i_motd.py
+++ b/envisage/examples/demo/MOTD/acme/motd/i_motd.py
@@ -16,10 +16,10 @@
 
 
 class IMOTD(Interface):
-    """ The 'Message of the Day' interface. """
+    """The 'Message of the Day' interface."""
 
     def motd(self):
-        """ Return the message of the day.
+        """Return the message of the day.
 
         Returns an object that implements the 'IMessage' interface.
 
diff --git a/envisage/examples/demo/MOTD/acme/motd/message.py b/envisage/examples/demo/MOTD/acme/motd/message.py
index 7d95c5cf4..a72455907 100644
--- a/envisage/examples/demo/MOTD/acme/motd/message.py
+++ b/envisage/examples/demo/MOTD/acme/motd/message.py
@@ -11,16 +11,16 @@
 """ The default implementation of the 'IMessage' interface. """
 
 
-# Enthought library imports.
-from traits.api import HasTraits, Str, provides
-
 # Local imports.
 from acme.motd.i_message import IMessage
 
+# Enthought library imports.
+from traits.api import HasTraits, provides, Str
+
 
 @provides(IMessage)
 class Message(HasTraits):
-    """ The default implementation of the 'IMessage' interface. """
+    """The default implementation of the 'IMessage' interface."""
 
     # The author of the message.
     author = Str
diff --git a/envisage/examples/demo/MOTD/acme/motd/motd.py b/envisage/examples/demo/MOTD/acme/motd/motd.py
index 8d05667f8..9fda11254 100644
--- a/envisage/examples/demo/MOTD/acme/motd/motd.py
+++ b/envisage/examples/demo/MOTD/acme/motd/motd.py
@@ -14,18 +14,18 @@
 # Standard library imports.
 from random import choice
 
-# Enthought library imports.
-from traits.api import HasTraits, List, provides
-
 # Local imports.
 from acme.motd.i_message import IMessage
 from acme.motd.i_motd import IMOTD
 from acme.motd.message import Message
 
+# Enthought library imports.
+from traits.api import HasTraits, List, provides
+
 
 @provides(IMOTD)
 class MOTD(HasTraits):
-    """ The 'Message of the Day' implementation! """
+    """The 'Message of the Day' implementation!"""
 
     # The default message is used when there are no other messages!
     DEFAULT_MESSAGE = Message(
@@ -40,7 +40,7 @@ class MOTD(HasTraits):
     ###########################################################################
 
     def motd(self):
-        """ Prints a random message. """
+        """Prints a random message."""
 
         if len(self.messages) > 0:
             message = choice(self.messages)
diff --git a/envisage/examples/demo/MOTD/acme/motd/motd_plugin.py b/envisage/examples/demo/MOTD/acme/motd/motd_plugin.py
index d4c4cb7d0..d66ba106e 100644
--- a/envisage/examples/demo/MOTD/acme/motd/motd_plugin.py
+++ b/envisage/examples/demo/MOTD/acme/motd/motd_plugin.py
@@ -20,13 +20,14 @@
 # Eveything else should be imported when it is actually required.
 
 
+from traits.api import Instance, List, on_trait_change
+
 # Enthought library imports.
 from envisage.api import ExtensionPoint, Plugin, ServiceOffer
-from traits.api import Instance, List, on_trait_change
 
 
 class MOTDPlugin(Plugin):
-    """ The 'Message of the Day' plugin.
+    """The 'Message of the Day' plugin.
 
     This plugin simply prints the 'Message of the Day' to stdout.
 
@@ -69,7 +70,7 @@ class MOTDPlugin(Plugin):
     service_offers = List(contributes_to=SERVICE_OFFERS)
 
     def _service_offers_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # Register the protocol as a string containing the actual module path
         # and *not* a module path that goes via an 'api.py' file as this does
@@ -89,7 +90,7 @@ def _service_offers_default(self):
     ###########################################################################
 
     def _create_motd_service(self):
-        """ Factory method for the 'MOTD' service. """
+        """Factory method for the 'MOTD' service."""
 
         # Only do imports when you need to! This makes sure that the import
         # only happens when somebody needs an 'IMOTD' service.
@@ -101,7 +102,7 @@ def _create_motd_service(self):
     # the application has started all of its plugins.
     @on_trait_change("application:started")
     def _print_motd(self):
-        """ Print the 'Message of the Day' to stdout! """
+        """Print the 'Message of the Day' to stdout!"""
 
         # Note that we always offer the service via its name, but look it up
         # via the actual protocol.
diff --git a/envisage/examples/demo/MOTD/acme/motd/software_quotes/software_quotes_plugin.py b/envisage/examples/demo/MOTD/acme/motd/software_quotes/software_quotes_plugin.py
index 8a4a21592..60d346051 100644
--- a/envisage/examples/demo/MOTD/acme/motd/software_quotes/software_quotes_plugin.py
+++ b/envisage/examples/demo/MOTD/acme/motd/software_quotes/software_quotes_plugin.py
@@ -11,13 +11,14 @@
 """ The 'Software Quotes' plugin """
 
 
+from traits.api import List
+
 # Enthought library imports.
 from envisage.api import Plugin
-from traits.api import List
 
 
 class SoftwareQuotesPlugin(Plugin):
-    """ The 'Software Quotes' plugin. """
+    """The 'Software Quotes' plugin."""
 
     #### 'IPlugin' interface ##################################################
 
@@ -37,7 +38,7 @@ class SoftwareQuotesPlugin(Plugin):
     messages = List(contributes_to="acme.motd.messages")
 
     def _messages_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # Only do imports when you need to!
         from acme.motd.software_quotes.messages import messages
diff --git a/envisage/examples/demo/MOTD/run.py b/envisage/examples/demo/MOTD/run.py
index 32338ea47..58652bad7 100644
--- a/envisage/examples/demo/MOTD/run.py
+++ b/envisage/examples/demo/MOTD/run.py
@@ -15,13 +15,14 @@
 
 
 def main():
-    """ Run the application. """
+    """Run the application."""
     # Import here so that this script can be run from anywhere without
     # having to install the packages.
     from acme.motd.motd_plugin import MOTDPlugin
     from acme.motd.software_quotes.software_quotes_plugin import (
         SoftwareQuotesPlugin,
     )
+
     # Create an application containing the appropriate plugins.
     application = Application(
         id="acme.motd",
diff --git a/envisage/examples/demo/plugins/tasks/attractors/attractors_application.py b/envisage/examples/demo/plugins/tasks/attractors/attractors_application.py
index 4c446c823..aa0a8aa0e 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/attractors_application.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/attractors_application.py
@@ -8,18 +8,18 @@
 #
 # Thanks for using Enthought open source!
 
-# Enthought library imports.
-from envisage.ui.tasks.api import TasksApplication
+# Local imports.
+from attractors.attractors_preferences import AttractorsPreferences
+
 from pyface.tasks.api import TaskWindowLayout
 from traits.api import Bool, Instance, List, Property
 
-# Local imports.
-from attractors.attractors_preferences import AttractorsPreferences
+# Enthought library imports.
+from envisage.ui.tasks.api import TasksApplication
 
 
 class AttractorsApplication(TasksApplication):
-    """ The chaotic attractors Tasks application.
-    """
+    """The chaotic attractors Tasks application."""
 
     #### 'IApplication' interface #############################################
 
diff --git a/envisage/examples/demo/plugins/tasks/attractors/attractors_plugin.py b/envisage/examples/demo/plugins/tasks/attractors/attractors_plugin.py
index 764366782..68332e671 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/attractors_plugin.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/attractors_plugin.py
@@ -11,15 +11,15 @@
 # Standard library imports.
 import os.path
 
+from traits.api import List
+
 # Enthought library imports.
 from envisage.api import Plugin
 from envisage.ui.tasks.api import TaskFactory
-from traits.api import List
 
 
 class AttractorsPlugin(Plugin):
-    """ The chaotic attractors plugin.
-    """
+    """The chaotic attractors plugin."""
 
     # Extension point IDs.
     PREFERENCES = "envisage.preferences"
diff --git a/envisage/examples/demo/plugins/tasks/attractors/attractors_preferences.py b/envisage/examples/demo/plugins/tasks/attractors/attractors_preferences.py
index ec5c00e8e..ecc2b18e8 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/attractors_preferences.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/attractors_preferences.py
@@ -8,16 +8,16 @@
 #
 # Thanks for using Enthought open source!
 
-# Enthought library imports.
-from envisage.ui.tasks.api import PreferencesPane
 from apptools.preferences.api import PreferencesHelper
 from traits.api import Bool, Dict, Str
-from traitsui.api import EnumEditor, HGroup, VGroup, Item, Label, View
+from traitsui.api import EnumEditor, HGroup, Item, Label, VGroup, View
+
+# Enthought library imports.
+from envisage.ui.tasks.api import PreferencesPane
 
 
 class AttractorsPreferences(PreferencesHelper):
-    """ The preferences helper for the Attractors application.
-    """
+    """The preferences helper for the Attractors application."""
 
     #### 'PreferencesHelper' interface ########################################
 
@@ -35,8 +35,7 @@ class AttractorsPreferences(PreferencesHelper):
 
 
 class AttractorsPreferencesPane(PreferencesPane):
-    """ The preferences pane for the Attractors application.
-    """
+    """The preferences pane for the Attractors application."""
 
     #### 'PreferencesPane' interface ##########################################
 
diff --git a/envisage/examples/demo/plugins/tasks/attractors/model/henon.py b/envisage/examples/demo/plugins/tasks/attractors/model/henon.py
index e6c4b883a..1f7a08349 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/model/henon.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/model/henon.py
@@ -10,29 +10,28 @@
 
 # System library imports.
 import numpy as np
+
+# Local imports.
+from attractors.model.i_plottable_2d import IPlottable2d
 from scipy import array, zeros
 
 # Enthought library imports.
 from traits.api import (
     Array,
+    cached_property,
     Float,
     HasTraits,
     Int,
     Property,
-    Str,
-    cached_property,
     provides,
+    Str,
 )
 from traitsui.api import Item, View
 
-# Local imports.
-from attractors.model.i_plottable_2d import IPlottable2d
-
 
 @provides(IPlottable2d)
 class Henon(HasTraits):
-    """ The model object for the Henon map.
-    """
+    """The model object for the Henon map."""
 
     #### 'Henon' interface ####################################################
 
@@ -75,7 +74,7 @@ def _get_points(self):
         points = zeros((self.steps, 2))
         for i in range(self.steps):
             x, y = points[i] = point
-            point = array([y + 1 - self.a * x ** 2, self.b * x])
+            point = array([y + 1 - self.a * x**2, self.b * x])
         return points
 
     @cached_property
diff --git a/envisage/examples/demo/plugins/tasks/attractors/model/i_model_2d.py b/envisage/examples/demo/plugins/tasks/attractors/model/i_model_2d.py
index 3771e6d4d..a4e0083c3 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/model/i_model_2d.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/model/i_model_2d.py
@@ -13,7 +13,6 @@
 
 
 class IModel2d(Interface):
-
     # The user-visible name of the model.
     name = Str()
 
diff --git a/envisage/examples/demo/plugins/tasks/attractors/model/i_model_3d.py b/envisage/examples/demo/plugins/tasks/attractors/model/i_model_3d.py
index 41c4f76a4..027afd54e 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/model/i_model_3d.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/model/i_model_3d.py
@@ -11,21 +11,20 @@
 # Enthought library imports.
 from traits.api import (
     Array,
+    cached_property,
     DelegatesTo,
     HasTraits,
-    Interface,
     Instance,
+    Interface,
     Property,
     Str,
     Trait,
-    cached_property,
 )
 from traitsui.api import Group, Item, View
 
 
 class IModel3d(Interface):
-    """ A model object that produces an array of 3D points.
-    """
+    """A model object that produces an array of 3D points."""
 
     # The user-visible name of the model.
     name = Str
@@ -35,7 +34,8 @@ class IModel3d(Interface):
 
 
 class IModel3dIPlottable2dMixin(HasTraits):
-    """ Mixin class to facilitate defining a IModel3d -> IPlottable2D adapter.
+    """
+    Mixin class to facilitate defining a IModel3d -> IPlottable2D adapter.
     """
 
     #### 'Adapter' interface ##################################################
diff --git a/envisage/examples/demo/plugins/tasks/attractors/model/i_plottable_2d.py b/envisage/examples/demo/plugins/tasks/attractors/model/i_plottable_2d.py
index 4eebce4e4..de812db38 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/model/i_plottable_2d.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/model/i_plottable_2d.py
@@ -8,15 +8,14 @@
 #
 # Thanks for using Enthought open source!
 
-# Enthought library imports.
-from traits.api import Enum, Str
-
 # Local imports.
 from attractors.model.i_model_2d import IModel2d
 
+# Enthought library imports.
+from traits.api import Enum, Str
 
-class IPlottable2d(IModel2d):
 
+class IPlottable2d(IModel2d):
     plot_type = Enum("line", "scatter")
 
     x_label = Str()
diff --git a/envisage/examples/demo/plugins/tasks/attractors/model/lorenz.py b/envisage/examples/demo/plugins/tasks/attractors/model/lorenz.py
index e787100c0..c75e568c6 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/model/lorenz.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/model/lorenz.py
@@ -10,6 +10,10 @@
 
 # System library imports.
 import numpy as np
+
+# Local imports
+from attractors.model.i_model_3d import IModel3d, IModel3dIPlottable2dMixin
+from attractors.model.i_plottable_2d import IPlottable2d
 from scipy import arange, array
 from scipy.integrate import odeint
 
@@ -17,26 +21,21 @@
 from traits.api import (
     Adapter,
     Array,
+    cached_property,
     Float,
     HasTraits,
     Instance,
     Property,
-    Str,
-    cached_property,
     provides,
     register_factory,
+    Str,
 )
-from traitsui.api import View, Item
-
-# Local imports
-from attractors.model.i_model_3d import IModel3d, IModel3dIPlottable2dMixin
-from attractors.model.i_plottable_2d import IPlottable2d
+from traitsui.api import Item, View
 
 
 @provides(IModel3d)
 class Lorenz(HasTraits):
-    """ The model object for the Lorenz attractor.
-    """
+    """The model object for the Lorenz attractor."""
 
     #### 'IModel3d' interface #################################################
 
@@ -100,7 +99,6 @@ def _get_times(self):
 
 @provides(IPlottable2d)
 class LorenzIPlottable2dAdapter(Adapter, IModel3dIPlottable2dMixin):
-
     adaptee = Instance(Lorenz)
 
     plot_type = Str("line")
diff --git a/envisage/examples/demo/plugins/tasks/attractors/model/rossler.py b/envisage/examples/demo/plugins/tasks/attractors/model/rossler.py
index 043e85a00..2fc314e9f 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/model/rossler.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/model/rossler.py
@@ -10,6 +10,10 @@
 
 # System library imports.
 import numpy as np
+
+# Local imports
+from attractors.model.i_model_3d import IModel3d, IModel3dIPlottable2dMixin
+from attractors.model.i_plottable_2d import IPlottable2d
 from scipy import arange, array
 from scipy.integrate import odeint
 
@@ -17,26 +21,21 @@
 from traits.api import (
     Adapter,
     Array,
+    cached_property,
     Float,
     HasTraits,
     Instance,
     Property,
-    Str,
-    cached_property,
     provides,
     register_factory,
+    Str,
 )
-from traitsui.api import View, Item
-
-# Local imports
-from attractors.model.i_model_3d import IModel3d, IModel3dIPlottable2dMixin
-from attractors.model.i_plottable_2d import IPlottable2d
+from traitsui.api import Item, View
 
 
 @provides(IModel3d)
 class Rossler(HasTraits):
-    """ The model object for the Rossler attractor.
-    """
+    """The model object for the Rossler attractor."""
 
     #### 'IModel3d' interface #################################################
 
@@ -92,7 +91,6 @@ def _get_times(self):
 
 @provides(IPlottable2d)
 class RosslerIPlottable2dAdapter(Adapter, IModel3dIPlottable2dMixin):
-
     adaptee = Instance(Rossler)
 
     plot_type = Str("line")
diff --git a/envisage/examples/demo/plugins/tasks/attractors/model_config_pane.py b/envisage/examples/demo/plugins/tasks/attractors/model_config_pane.py
index e80ba0336..94a409182 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/model_config_pane.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/model_config_pane.py
@@ -15,8 +15,8 @@
 
 
 class ModelConfigPane(TraitsDockPane):
-    """ A simple dock pane for editing an attractor model's configuration
-        options.
+    """A simple dock pane for editing an attractor model's configuration
+    options.
     """
 
     #### 'ITaskPane' interface ################################################
diff --git a/envisage/examples/demo/plugins/tasks/attractors/model_help_pane.py b/envisage/examples/demo/plugins/tasks/attractors/model_help_pane.py
index 9f938a1b1..107ce8c8c 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/model_help_pane.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/model_help_pane.py
@@ -14,7 +14,7 @@
 
 # Enthought library imports.
 from pyface.tasks.api import TraitsDockPane
-from traits.api import HasTraits, Instance, Property, Str, cached_property
+from traits.api import cached_property, HasTraits, Instance, Property, Str
 from traitsui.api import HTMLEditor, Item, View
 
 # Constants.
@@ -22,8 +22,7 @@
 
 
 class ModelHelpPane(TraitsDockPane):
-    """ A dock pane for viewing any help associated with a model.
-    """
+    """A dock pane for viewing any help associated with a model."""
 
     #### 'ITaskPane' interface ################################################
 
@@ -52,8 +51,7 @@ class ModelHelpPane(TraitsDockPane):
 
     @cached_property
     def _get_html(self):
-        """ Fetch the help HTML for the current model.
-        """
+        """Fetch the help HTML for the current model."""
         if self.model is None:
             return "No model selected."
 
diff --git a/envisage/examples/demo/plugins/tasks/attractors/plot_2d_pane.py b/envisage/examples/demo/plugins/tasks/attractors/plot_2d_pane.py
index 222914a21..2b7017e10 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/plot_2d_pane.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/plot_2d_pane.py
@@ -8,27 +8,27 @@
 #
 # Thanks for using Enthought open source!
 
+# Local imports.
+from attractors.model.i_plottable_2d import IPlottable2d
+
 # Enthought library imports.
 from chaco.api import ArrayPlotData, Plot
 from enable.api import ComponentEditor
+
 from pyface.tasks.api import TraitsTaskPane
 from traits.api import (
     Dict,
     Instance,
     List,
-    Property,
-    Str,
     observe,
     on_trait_change,
+    Property,
+    Str,
 )
 from traitsui.api import EnumEditor, HGroup, Item, Label, UItem, View
 
-# Local imports.
-from attractors.model.i_plottable_2d import IPlottable2d
-
 
 class Plot2dPane(TraitsTaskPane):
-
     #### 'ITaskPane' interface ################################################
 
     id = "example.attractors.plot_2d_pane"
@@ -56,8 +56,8 @@ def _plot_default(self):
             ("x", "y"),
             type=self.plot_type,
             name=self.title,
-            marker='pixel',
-            color="blue"
+            marker="pixel",
+            color="blue",
         )
 
         return plot
@@ -89,8 +89,8 @@ def _update_plot_new_model(self, event):
             ("x", "y"),
             type=self.plot_type,
             name=self.title,
-            marker='pixel',
-            color="blue"
+            marker="pixel",
+            color="blue",
         )
         self.plot.invalidate_and_redraw()
 
@@ -100,9 +100,7 @@ def _update_plot_new_model(self, event):
             Item("active_model", editor=EnumEditor(name="_enum_map")),
             show_labels=False,
         ),
-        UItem(
-            "plot", editor=ComponentEditor()
-        ),
+        UItem("plot", editor=ComponentEditor()),
         resizable=True,
     )
 
diff --git a/envisage/examples/demo/plugins/tasks/attractors/plot_3d_pane.py b/envisage/examples/demo/plugins/tasks/attractors/plot_3d_pane.py
index e7a1feef0..93fc88459 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/plot_3d_pane.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/plot_3d_pane.py
@@ -8,26 +8,20 @@
 #
 # Thanks for using Enthought open source!
 
+# Local imports.
+from attractors.model.i_model_3d import IModel3d
+from mayavi.core.ui.mayavi_scene import MayaviScene
+
 # Enthought library imports.
 from mayavi.tools.mlab_scene_model import MlabSceneModel
-from mayavi.core.ui.mayavi_scene import MayaviScene
-from pyface.tasks.api import TraitsTaskPane
-from traits.api import (
-    Dict,
-    Instance,
-    List,
-    Str,
-    on_trait_change,
-)
-from traitsui.api import EnumEditor, HGroup, Item, Label, View
 from tvtk.pyface.scene_editor import SceneEditor
 
-# Local imports.
-from attractors.model.i_model_3d import IModel3d
+from pyface.tasks.api import TraitsTaskPane
+from traits.api import Dict, Instance, List, on_trait_change, Str
+from traitsui.api import EnumEditor, HGroup, Item, Label, View
 
 
 class Plot3dPane(TraitsTaskPane):
-
     #### 'ITaskPane' interface ################################################
 
     id = "example.attractors.plot_3d_pane"
diff --git a/envisage/examples/demo/plugins/tasks/attractors/visualize_2d_task.py b/envisage/examples/demo/plugins/tasks/attractors/visualize_2d_task.py
index eb7d0365b..54cc2fd1a 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/visualize_2d_task.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/visualize_2d_task.py
@@ -8,21 +8,20 @@
 #
 # Thanks for using Enthought open source!
 
-# Enthought library imports.
-from pyface.tasks.action.api import SMenu, SMenuBar, TaskToggleGroup
-from pyface.tasks.api import Task, TaskLayout, Tabbed, PaneItem
-from traits.api import Any, Instance, List, adapt
-
 # Local imports.
 from attractors.model.i_plottable_2d import IPlottable2d
 from attractors.model_config_pane import ModelConfigPane
 from attractors.model_help_pane import ModelHelpPane
 from attractors.plot_2d_pane import Plot2dPane
 
+# Enthought library imports.
+from pyface.tasks.action.api import SMenu, SMenuBar, TaskToggleGroup
+from pyface.tasks.api import PaneItem, Tabbed, Task, TaskLayout
+from traits.api import adapt, Any, Instance, List
+
 
 class Visualize2dTask(Task):
-    """ A task for visualizing attractors in 2D.
-    """
+    """A task for visualizing attractors in 2D."""
 
     #### 'Task' interface #####################################################
 
@@ -49,8 +48,8 @@ class Visualize2dTask(Task):
     ###########################################################################
 
     def create_central_pane(self):
-        """ Create a plot pane with a list of models. Keep track of which model
-            is active so that dock panes can introspect it.
+        """Create a plot pane with a list of models. Keep track of which model
+        is active so that dock panes can introspect it.
         """
         pane = Plot2dPane(models=self.models)
 
diff --git a/envisage/examples/demo/plugins/tasks/attractors/visualize_3d_task.py b/envisage/examples/demo/plugins/tasks/attractors/visualize_3d_task.py
index f9af26d75..697e154f7 100644
--- a/envisage/examples/demo/plugins/tasks/attractors/visualize_3d_task.py
+++ b/envisage/examples/demo/plugins/tasks/attractors/visualize_3d_task.py
@@ -8,20 +8,19 @@
 #
 # Thanks for using Enthought open source!
 
-# Enthought library imports.
-from pyface.tasks.action.api import SMenu, SMenuBar, TaskToggleGroup
-from pyface.tasks.api import Task, TaskLayout, Tabbed, PaneItem
-from traits.api import Any, List
-
 # Local imports.
 from attractors.model_config_pane import ModelConfigPane
 from attractors.model_help_pane import ModelHelpPane
 from attractors.plot_3d_pane import Plot3dPane
 
+# Enthought library imports.
+from pyface.tasks.action.api import SMenu, SMenuBar, TaskToggleGroup
+from pyface.tasks.api import PaneItem, Tabbed, Task, TaskLayout
+from traits.api import Any, List
+
 
 class Visualize3dTask(Task):
-    """ A task for visualizing attractors in 3D.
-    """
+    """A task for visualizing attractors in 3D."""
 
     #### 'Task' interface #####################################################
 
@@ -48,8 +47,8 @@ class Visualize3dTask(Task):
     ###########################################################################
 
     def create_central_pane(self):
-        """ Create a plot pane with a list of models. Keep track of which model
-            is active so that dock panes can introspect it.
+        """Create a plot pane with a list of models. Keep track of which model
+        is active so that dock panes can introspect it.
         """
         pane = Plot3dPane(models=self.models)
 
diff --git a/envisage/examples/demo/plugins/tasks/run_attractor.py b/envisage/examples/demo/plugins/tasks/run_attractor.py
index b9985f8a7..f179ce4c1 100644
--- a/envisage/examples/demo/plugins/tasks/run_attractor.py
+++ b/envisage/examples/demo/plugins/tasks/run_attractor.py
@@ -14,12 +14,11 @@
 
 
 def main(argv):
-    """ Run the application.
-    """
+    """Run the application."""
     # Import here so that this script can be run from anywhere without
     # having to install the packages.
-    from attractors.attractors_plugin import AttractorsPlugin
     from attractors.attractors_application import AttractorsApplication
+    from attractors.attractors_plugin import AttractorsPlugin
 
     plugins = [CorePlugin(), TasksPlugin(), AttractorsPlugin()]
     app = AttractorsApplication(plugins=plugins)
@@ -28,6 +27,7 @@ def main(argv):
 
 if __name__ == "__main__":
     import sys
+
     # This context manager is added so that one can run this example from any
     # directory without necessarily having installed the examples as packages.
     from envisage.examples._demo import demo_path
diff --git a/envisage/examples/tests/test__demo.py b/envisage/examples/tests/test__demo.py
index 61704190c..fc6ec212a 100644
--- a/envisage/examples/tests/test__demo.py
+++ b/envisage/examples/tests/test__demo.py
@@ -15,7 +15,7 @@
 
 
 class TestDemoUtilities(unittest.TestCase):
-    """ Test utility functions in the _demo module."""
+    """Test utility functions in the _demo module."""
 
     def test_sys_path_inserted(self):
         path = os.path.join("dirname", "file.py")
diff --git a/envisage/examples/tests/test_etsdemo_info.py b/envisage/examples/tests/test_etsdemo_info.py
index 3a17f0f5e..4a964b783 100644
--- a/envisage/examples/tests/test_etsdemo_info.py
+++ b/envisage/examples/tests/test_etsdemo_info.py
@@ -14,8 +14,7 @@
 
 
 class TestETSDemoInfo(unittest.TestCase):
-
     def test_info(self):
         # input to info is currently just a placeholder
         response = info({})
-        self.assertTrue(os.path.exists(response['root']))
+        self.assertTrue(os.path.exists(response["root"]))
diff --git a/envisage/extension_point.py b/envisage/extension_point.py
index 7606ccce8..982fa9053 100644
--- a/envisage/extension_point.py
+++ b/envisage/extension_point.py
@@ -15,12 +15,11 @@
 import weakref
 
 # Enthought library imports.
-from traits.api import List, TraitType, Undefined, provides
+from traits.api import List, provides, TraitType, Undefined
 
 # Local imports.
 from .i_extension_point import IExtensionPoint
 
-
 # Exception message template.
 INVALID_TRAIT_TYPE = (
     'extension points must be "List"s e.g. List, List(Int)'
@@ -32,7 +31,7 @@
 # declare that we implement an interface.
 @provides(IExtensionPoint)
 class ExtensionPoint(TraitType):
-    """ A trait type used to declare and access extension points.
+    """A trait type used to declare and access extension points.
 
     Note that this is a trait *type* and hence does *NOT* have traits itself
     (i.e. it does *not* inherit from 'HasTraits').
@@ -45,14 +44,14 @@ class ExtensionPoint(TraitType):
 
     @staticmethod
     def connect_extension_point_traits(obj):
-        """ Connect all of the 'ExtensionPoint' traits on an object. """
+        """Connect all of the 'ExtensionPoint' traits on an object."""
 
         for trait_name, trait in obj.traits(__extension_point__=True).items():
             trait.trait_type.connect(obj, trait_name)
 
     @staticmethod
     def disconnect_extension_point_traits(obj):
-        """ Disconnect all of the 'ExtensionPoint' traits on an object. """
+        """Disconnect all of the 'ExtensionPoint' traits on an object."""
 
         for trait_name, trait in obj.traits(__extension_point__=True).items():
             trait.trait_type.disconnect(obj, trait_name)
@@ -62,7 +61,7 @@ def disconnect_extension_point_traits(obj):
     ###########################################################################
 
     def __init__(self, trait_type=List, id=None, **metadata):
-        """ Constructor. """
+        """Constructor."""
 
         # We add '__extension_point__' to the metadata to make the extension
         # point traits easier to find with the 'traits' and 'trait_names'
@@ -98,7 +97,7 @@ def __init__(self, trait_type=List, id=None, **metadata):
         self._obj_to_listeners_map = weakref.WeakKeyDictionary()
 
     def __repr__(self):
-        """ String representation of an ExtensionPoint object """
+        """String representation of an ExtensionPoint object"""
         return "ExtensionPoint(id={!r})".format(self.id)
 
     ###########################################################################
@@ -106,7 +105,7 @@ def __repr__(self):
     ###########################################################################
 
     def get(self, obj, trait_name):
-        """ Trait type getter. """
+        """Trait type getter."""
 
         extension_registry = self._get_extension_registry(obj)
 
@@ -117,7 +116,7 @@ def get(self, obj, trait_name):
         return self.trait_type.validate(obj, trait_name, extensions)
 
     def set(self, obj, name, value):
-        """ Trait type setter. """
+        """Trait type setter."""
 
         extension_registry = self._get_extension_registry(obj)
 
@@ -131,7 +130,7 @@ def set(self, obj, name, value):
     ###########################################################################
 
     def connect(self, obj, trait_name):
-        """ Connect the extension point to a trait on an object.
+        """Connect the extension point to a trait on an object.
 
         This allows the object to react when contributions are added or
         removed from the extension point.
@@ -143,7 +142,7 @@ def connect(self, obj, trait_name):
         """
 
         def listener(extension_registry, event):
-            """ Listener called when an extension point is changed. """
+            """Listener called when an extension point is changed."""
 
             # If an index was specified then we fire an '_items' changed event.
             if event.index is not None:
@@ -170,7 +169,7 @@ def listener(extension_registry, event):
         listeners[trait_name] = listener
 
     def disconnect(self, obj, trait_name):
-        """ Disconnect the extension point from a trait on an object. """
+        """Disconnect the extension point from a trait on an object."""
 
         extension_registry = self._get_extension_registry(obj)
 
@@ -189,7 +188,7 @@ def disconnect(self, obj, trait_name):
     ###########################################################################
 
     def _get_extension_registry(self, obj):
-        """ Return the extension registry in effect for an object. """
+        """Return the extension registry in effect for an object."""
 
         extension_registry = getattr(obj, "extension_registry", None)
         if extension_registry is None:
diff --git a/envisage/extension_point_binding.py b/envisage/extension_point_binding.py
index 5682081cb..f15e413cb 100644
--- a/envisage/extension_point_binding.py
+++ b/envisage/extension_point_binding.py
@@ -18,7 +18,7 @@
 
 
 class ExtensionPointBinding(HasTraits):
-    """ A binding between a trait on an object and an extension point. """
+    """A binding between a trait on an object and an extension point."""
 
     #### 'ExtensionPointBinding' *CLASS* interface ############################
 
@@ -51,7 +51,7 @@ class ExtensionPointBinding(HasTraits):
     ###########################################################################
 
     def __init__(self, **traits):
-        """ Constructor. """
+        """Constructor."""
 
         super().__init__(**traits)
 
@@ -68,13 +68,13 @@ def __init__(self, **traits):
     #### Trait change handlers ################################################
 
     def _on_trait_changed(self, obj, trait_name, old, new):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         if not self._event_handled:
             self._set_extensions(new)
 
     def _on_trait_items_changed(self, obj, trait_name, old, event):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         if not self._event_handled:
             self._set_extensions(getattr(obj, self.trait_name))
@@ -82,7 +82,7 @@ def _on_trait_items_changed(self, obj, trait_name, old, event):
     #### Other observer pattern listeners #####################################
 
     def _extension_point_listener(self, extension_registry, event):
-        """ Listener called when an extension point is changed. """
+        """Listener called when an extension point is changed."""
 
         self._event_handled = True
         if event.index is not None:
@@ -95,7 +95,7 @@ def _extension_point_listener(self, extension_registry, event):
     #### Methods ##############################################################
 
     def _bind(self):
-        """ Wire-up trait change handlers etc. """
+        """Wire-up trait change handlers etc."""
 
         # Listen for the object's trait being changed.
         self.obj.on_trait_change(self._on_trait_changed, self.trait_name)
@@ -127,7 +127,7 @@ def _unbind(self):
         )
 
     def _set_trait(self, notify):
-        """ Set the object's trait to the value of the extension point. """
+        """Set the object's trait to the value of the extension point."""
 
         value = self.extension_registry.get_extensions(self.extension_point_id)
         traits = {self.trait_name: value}
@@ -135,7 +135,7 @@ def _set_trait(self, notify):
         self.obj.trait_set(trait_change_notify=notify, **traits)
 
     def _update_trait(self, event):
-        """ Update the object's trait to the value of the extension point. """
+        """Update the object's trait to the value of the extension point."""
 
         self._set_trait(notify=False)
 
@@ -144,7 +144,7 @@ def _update_trait(self, event):
         )
 
     def _set_extensions(self, extensions):
-        """ Set the extensions to an extension point. """
+        """Set the extensions to an extension point."""
 
         self.extension_registry.set_extensions(
             self.extension_point_id, extensions
diff --git a/envisage/extension_point_changed_event.py b/envisage/extension_point_changed_event.py
index ebcbbe00a..d16b6583a 100644
--- a/envisage/extension_point_changed_event.py
+++ b/envisage/extension_point_changed_event.py
@@ -15,10 +15,10 @@
 
 
 class ExtensionPointChangedEvent(TraitListEvent):
-    """ An event fired when an extension point's extensions have changed. """
+    """An event fired when an extension point's extensions have changed."""
 
     def __init__(self, extension_point_id=None, **kw):
-        """ Constructor. """
+        """Constructor."""
 
         # The base class has the 'index', 'removed' and 'added' attributes.
         super().__init__(**kw)
@@ -27,9 +27,7 @@ def __init__(self, extension_point_id=None, **kw):
         self.extension_point_id = extension_point_id
 
     def __repr__(self):
-        return ("ExtensionPointChangedEvent(extension_point_id={!r}, "
-                "index={!r}, removed={!r}, added={!r})").format(
-                    self.extension_point_id,
-                    self.index,
-                    self.removed,
-                    self.added)
+        return (
+            "ExtensionPointChangedEvent(extension_point_id={!r}, "
+            "index={!r}, removed={!r}, added={!r})"
+        ).format(self.extension_point_id, self.index, self.removed, self.added)
diff --git a/envisage/extension_provider.py b/envisage/extension_provider.py
index 7944eb7b3..c14aefcb1 100644
--- a/envisage/extension_provider.py
+++ b/envisage/extension_provider.py
@@ -20,7 +20,7 @@
 
 @provides(IExtensionProvider)
 class ExtensionProvider(HasTraits):
-    """ The default base class for extension providers. """
+    """The default base class for extension providers."""
 
     #### 'IExtensionProvider' interface #######################################
 
@@ -30,12 +30,12 @@ class ExtensionProvider(HasTraits):
     extension_point_changed = Event(ExtensionPointChangedEvent)
 
     def get_extension_points(self):
-        """ Return the extension points offered by the provider. """
+        """Return the extension points offered by the provider."""
 
         return []
 
     def get_extensions(self, extension_point_id):
-        """ Return the provider's extensions to an extension point. """
+        """Return the provider's extensions to an extension point."""
 
         return []
 
@@ -44,7 +44,7 @@ def get_extensions(self, extension_point_id):
     def _fire_extension_point_changed(
         self, extension_point_id, added, removed, index
     ):
-        """ Fire an extension point changed event. """
+        """Fire an extension point changed event."""
 
         self.extension_point_changed = ExtensionPointChangedEvent(
             extension_point_id=extension_point_id,
diff --git a/envisage/extension_registry.py b/envisage/extension_registry.py
index e82e84be5..d382409d3 100644
--- a/envisage/extension_registry.py
+++ b/envisage/extension_registry.py
@@ -23,7 +23,6 @@
 from .i_extension_registry import IExtensionRegistry
 from .unknown_extension_point import UnknownExtensionPoint
 
-
 # Logging.
 logger = logging.getLogger(__name__)
 
@@ -63,7 +62,7 @@ def _saferef(listener):
 
 @provides(IExtensionRegistry)
 class ExtensionRegistry(HasTraits):
-    """ A base class for extension registry implementation. """
+    """A base class for extension registry implementation."""
 
     ###########################################################################
     # Protected 'ExtensionRegistry' interface.
@@ -93,42 +92,42 @@ class ExtensionRegistry(HasTraits):
     ###########################################################################
 
     def add_extension_point_listener(self, listener, extension_point_id=None):
-        """ Add a listener for extensions being added or removed. """
+        """Add a listener for extensions being added or removed."""
 
         listeners = self._listeners.setdefault(extension_point_id, [])
         listeners.append(_saferef(listener))
 
     def add_extension_point(self, extension_point):
-        """ Add an extension point. """
+        """Add an extension point."""
 
         self._extension_points[extension_point.id] = extension_point
         logger.debug("extension point <%s> added", extension_point.id)
 
     def get_extensions(self, extension_point_id):
-        """ Return the extensions contributed to an extension point. """
+        """Return the extensions contributed to an extension point."""
 
         return self._get_extensions(extension_point_id)[:]
 
     def get_extension_point(self, extension_point_id):
-        """ Return the extension point with the specified Id. """
+        """Return the extension point with the specified Id."""
 
         return self._extension_points.get(extension_point_id)
 
     def get_extension_points(self):
-        """ Return all extension points. """
+        """Return all extension points."""
 
         return list(self._extension_points.values())
 
     def remove_extension_point_listener(
         self, listener, extension_point_id=None
     ):
-        """ Remove a listener for extensions being added or removed. """
+        """Remove a listener for extensions being added or removed."""
 
         listeners = self._listeners.setdefault(extension_point_id, [])
         listeners.remove(_saferef(listener))
 
     def remove_extension_point(self, extension_point_id):
-        """ Remove an extension point. """
+        """Remove an extension point."""
 
         self._check_extension_point(extension_point_id)
 
@@ -149,7 +148,7 @@ def remove_extension_point(self, extension_point_id):
         logger.debug("extension point <%s> removed", extension_point_id)
 
     def set_extensions(self, extension_point_id, extensions):
-        """ Set the extensions contributed to an extension point. """
+        """Set the extensions contributed to an extension point."""
 
         self._check_extension_point(extension_point_id)
 
@@ -164,7 +163,7 @@ def set_extensions(self, extension_point_id, extensions):
     ###########################################################################
 
     def _call_listeners(self, refs, extension_point_id, added, removed, index):
-        """ Call listeners that are listening to an extension point. """
+        """Call listeners that are listening to an extension point."""
 
         event = ExtensionPointChangedEvent(
             extension_point_id=extension_point_id,
@@ -179,7 +178,7 @@ def _call_listeners(self, refs, extension_point_id, added, removed, index):
                 listener(self, event)
 
     def _check_extension_point(self, extension_point_id):
-        """ Check to see if the extension point exists.
+        """Check to see if the extension point exists.
 
         Raise an 'UnknownExtensionPoint' if it does not.
 
@@ -189,12 +188,12 @@ def _check_extension_point(self, extension_point_id):
             raise UnknownExtensionPoint(extension_point_id)
 
     def _get_extensions(self, extension_point_id):
-        """ Return the extensions for the given extension point. """
+        """Return the extensions for the given extension point."""
 
         return self._extensions.setdefault(extension_point_id, [])
 
     def _get_listener_refs(self, extension_point_id):
-        """ Get weak references to all listeners to an extension point.
+        """Get weak references to all listeners to an extension point.
 
         Returns a list containing the weak references to those listeners that
         are listening to this extension point specifically first, followed by
diff --git a/envisage/i_application.py b/envisage/i_application.py
index 362cd0110..b834dccd0 100644
--- a/envisage/i_application.py
+++ b/envisage/i_application.py
@@ -14,18 +14,19 @@
 from apptools.preferences.api import IPreferences
 from traits.api import Event, Instance, Str, VetoableEvent
 
+from .application_event import ApplicationEvent
+
 # Local imports.
 from .i_extension_registry import IExtensionRegistry
 from .i_import_manager import IImportManager
 from .i_plugin_manager import IPluginManager
 from .i_service_registry import IServiceRegistry
-from .application_event import ApplicationEvent
 
 
 class IApplication(
     IExtensionRegistry, IImportManager, IPluginManager, IServiceRegistry
 ):
-    """ The application interface. """
+    """The application interface."""
 
     #: The application's globally unique identifier.
     id = Str
@@ -60,7 +61,7 @@ class IApplication(
     stopped = Event(ApplicationEvent)
 
     def run(self):
-        """ Run the application.
+        """Run the application.
 
         The same as::
 
diff --git a/envisage/i_extension_point.py b/envisage/i_extension_point.py
index cc85221e8..66c7774e0 100644
--- a/envisage/i_extension_point.py
+++ b/envisage/i_extension_point.py
@@ -15,7 +15,7 @@
 
 
 class IExtensionPoint(Interface):
-    """ The interface for extension points. """
+    """The interface for extension points."""
 
     # A description of what the extension point is and does! (it is called
     # the slightly dubious, 'desc', instead of 'description', or, to be more
diff --git a/envisage/i_extension_point_user.py b/envisage/i_extension_point_user.py
index c1281796f..e7cc054bf 100644
--- a/envisage/i_extension_point_user.py
+++ b/envisage/i_extension_point_user.py
@@ -18,7 +18,7 @@
 
 
 class IExtensionPointUser(Interface):
-    """ The interface for objects using the 'ExtensionPoint' trait type. """
+    """The interface for objects using the 'ExtensionPoint' trait type."""
 
     # The extension registry that the object's extension points are stored in.
     extension_registry = Instance(IExtensionRegistry)
diff --git a/envisage/i_extension_provider.py b/envisage/i_extension_provider.py
index efdd225a2..408ca1e89 100644
--- a/envisage/i_extension_provider.py
+++ b/envisage/i_extension_provider.py
@@ -18,13 +18,13 @@
 
 
 class IExtensionProvider(Interface):
-    """ The interface for extension providers. """
+    """The interface for extension providers."""
 
     # The event fired when one of the provider's extension points has changed.
     extension_point_changed = Event(ExtensionPointChangedEvent)
 
     def get_extension_points(self):
-        """ Return the extension points offered by the provider.
+        """Return the extension points offered by the provider.
 
         Return an empty list if the provider does not offer any extension
         points.
@@ -32,7 +32,7 @@ def get_extension_points(self):
         """
 
     def get_extensions(self, extension_point_id):
-        """ Return the provider's extensions to an extension point.
+        """Return the provider's extensions to an extension point.
 
         The return value *must* be a list. Return an empty list if the provider
         does not contribute any extensions to the extension point.
diff --git a/envisage/i_extension_registry.py b/envisage/i_extension_registry.py
index 87a35e0d1..a391a9a32 100644
--- a/envisage/i_extension_registry.py
+++ b/envisage/i_extension_registry.py
@@ -15,10 +15,10 @@
 
 
 class IExtensionRegistry(Interface):
-    """ The interface for extension registries. """
+    """The interface for extension registries."""
 
     def add_extension_point_listener(self, listener, extension_point_id=None):
-        """ Add a listener for extensions being added or removed.
+        """Add a listener for extensions being added or removed.
 
         A listener is any Python callable with the following signature::
 
@@ -41,7 +41,7 @@ def listener(extension_registry, extension_point_changed_event):
         """
 
     def add_extension_point(self, extension_point):
-        """ Add an extension point.
+        """Add an extension point.
 
         If an extension point already exists with this Id then it is simply
         replaced.
@@ -49,35 +49,33 @@ def add_extension_point(self, extension_point):
         """
 
     def get_extensions(self, extension_point_id):
-        """ Return the extensions contributed to an extension point.
+        """Return the extensions contributed to an extension point.
 
         Return an empty list if the extension point does not exist.
 
         """
 
     def get_extension_point(self, extension_point_id):
-        """ Return the extension point with the specified Id.
+        """Return the extension point with the specified Id.
 
         Return None if no such extension point exists.
 
         """
 
     def get_extension_points(self):
-        """ Return all extension points that have been added to the registry.
-
-        """
+        """Return all extension points that have been added to the registry."""
 
     def remove_extension_point_listener(
         self, listener, extension_point_id=None
     ):
-        """ Remove a listener for extensions being added or removed.
+        """Remove a listener for extensions being added or removed.
 
         Raise a 'ValueError' if the listener does not exist.
 
         """
 
     def remove_extension_point(self, extension_point_id):
-        """ Remove an extension point.
+        """Remove an extension point.
 
         Raise an 'UnknownExtensionPoint' exception if no extension point exists
         with the specified Id.
@@ -85,6 +83,4 @@ def remove_extension_point(self, extension_point_id):
         """
 
     def set_extensions(self, extension_point_id, extensions):
-        """ Set the extensions contributed to an extension point.
-
-        """
+        """Set the extensions contributed to an extension point."""
diff --git a/envisage/i_import_manager.py b/envisage/i_import_manager.py
index d83d6965c..7699e231b 100644
--- a/envisage/i_import_manager.py
+++ b/envisage/i_import_manager.py
@@ -15,10 +15,10 @@
 
 
 class IImportManager(Interface):
-    """ The interface for import managers. """
+    """The interface for import managers."""
 
     def import_symbol(self, symbol_path):
-        """ Import the symbol defined by the specified symbol path.
+        """Import the symbol defined by the specified symbol path.
 
         'symbol_path' is a string containing the path to a symbol through the
         Python package namespace.
diff --git a/envisage/i_plugin.py b/envisage/i_plugin.py
index 3013eff8c..4a441a349 100644
--- a/envisage/i_plugin.py
+++ b/envisage/i_plugin.py
@@ -18,7 +18,7 @@
 
 
 class IPlugin(Interface):
-    """ The plugin interface. """
+    """The plugin interface."""
 
     #: The activator used to start and stop the plugin.
     activator = Instance(IPluginActivator)
@@ -42,7 +42,7 @@ class IPlugin(Interface):
     name = Str
 
     def start(self):
-        """ Start the plugin.
+        """Start the plugin.
 
         This method is called by the framework when the application is starting
         up. If you want to start a plugin manually use::
@@ -52,7 +52,7 @@ def start(self):
         """
 
     def stop(self):
-        """ Stop the plugin.
+        """Stop the plugin.
 
         This method is called by the framework when the application is
         stopping. If you want to stop a plugin manually use::
diff --git a/envisage/i_plugin_activator.py b/envisage/i_plugin_activator.py
index 58dcf41af..155c09416 100644
--- a/envisage/i_plugin_activator.py
+++ b/envisage/i_plugin_activator.py
@@ -15,7 +15,7 @@
 
 
 class IPluginActivator(Interface):
-    """ The plugin activator interface.
+    """The plugin activator interface.
 
     A plugin activator is really just a collection of two strategies - one
     to start the plugin and one to stop it.
@@ -31,11 +31,7 @@ class IPluginActivator(Interface):
     """
 
     def start_plugin(self, plugin):
-        """ Start the specified plugin.
-
-        """
+        """Start the specified plugin."""
 
     def stop_plugin(self, plugin):
-        """ Stop the specified plugin.
-
-        """
+        """Stop the specified plugin."""
diff --git a/envisage/i_plugin_manager.py b/envisage/i_plugin_manager.py
index f4bf47220..2b5e4228c 100644
--- a/envisage/i_plugin_manager.py
+++ b/envisage/i_plugin_manager.py
@@ -18,7 +18,7 @@
 
 
 class IPluginManager(Interface):
-    """ The plugin manager interface. """
+    """The plugin manager interface."""
 
     #### Events ####
 
@@ -29,36 +29,30 @@ class IPluginManager(Interface):
     plugin_removed = Event(PluginEvent)
 
     def __iter__(self):
-        """ Return an iterator over the manager's plugins.
-
-        """
+        """Return an iterator over the manager's plugins."""
 
     def add_plugin(self, plugin):
-        """ Add a plugin to the manager.
-
-        """
+        """Add a plugin to the manager."""
 
     def get_plugin(self, plugin_id):
-        """ Return the plugin with the specified Id.
+        """Return the plugin with the specified Id.
 
         Return None if no such plugin exists.
 
         """
 
     def remove_plugin(self, plugin):
-        """ Remove a plugin from the manager.
-
-        """
+        """Remove a plugin from the manager."""
 
     def start(self):
-        """ Start the plugin manager.
+        """Start the plugin manager.
 
         This starts all of the manager's plugins.
 
         """
 
     def start_plugin(self, plugin=None, plugin_id=None):
-        """ Start the specified plugin.
+        """Start the specified plugin.
 
         If a plugin is specified then start it.
 
@@ -69,7 +63,7 @@ def start_plugin(self, plugin=None, plugin_id=None):
         """
 
     def stop(self):
-        """ Stop the plugin manager.
+        """Stop the plugin manager.
 
         This stop's all of the plugin manager's plugins (in the reverse order
         that they were started).
@@ -77,7 +71,7 @@ def stop(self):
         """
 
     def stop_plugin(self, plugin=None, plugin_id=None):
-        """ Stop the specified plugin.
+        """Stop the specified plugin.
 
         If a plugin is specified then stop it (the Id is ignored).
 
diff --git a/envisage/i_provider_extension_registry.py b/envisage/i_provider_extension_registry.py
index 88aab6509..38efa79e3 100644
--- a/envisage/i_provider_extension_registry.py
+++ b/envisage/i_provider_extension_registry.py
@@ -15,20 +15,16 @@
 
 
 class IProviderExtensionRegistry(IExtensionRegistry):
-    """ The provider extension registry interface. """
+    """The provider extension registry interface."""
 
     def add_provider(self, provider):
-        """ Add an extension provider.
-
-        """
+        """Add an extension provider."""
 
     def get_providers(self):
-        """ Return all of the providers in the registry.
-
-        """
+        """Return all of the providers in the registry."""
 
     def remove_provider(self, provider):
-        """ Remove an extension provider.
+        """Remove an extension provider.
 
         Raise a 'ValueError' if the provider is not in the registry.
 
diff --git a/envisage/i_service_registry.py b/envisage/i_service_registry.py
index bb9268dcd..0e3ba0d30 100644
--- a/envisage/i_service_registry.py
+++ b/envisage/i_service_registry.py
@@ -15,7 +15,7 @@
 
 
 class IServiceRegistry(Interface):
-    """ The service registry interface.
+    """The service registry interface.
 
     The service registry provides a 'Yellow Pages' style mechanism, in that
     services are published and looked up by protocol (meaning, *interface*,
@@ -40,7 +40,7 @@ class IServiceRegistry(Interface):
     unregistered = Event
 
     def get_service(self, protocol, query="", minimize="", maximize=""):
-        """ Return at most one service that matches the specified query.
+        """Return at most one service that matches the specified query.
 
         The protocol can be an actual class or interface, or the *name* of a
         class or interface in the form '<module_name>.<class_name>'.
@@ -56,14 +56,14 @@ class or interface in the form '<module_name>.<class_name>'.
         """
 
     def get_service_from_id(self, service_id):
-        """ Return the service with the specified id.
+        """Return the service with the specified id.
 
         If no such service exists a 'ValueError' exception is raised.
 
         """
 
     def get_services(self, protocol, query="", minimize="", maximize=""):
-        """ Return all services that match the specified query.
+        """Return all services that match the specified query.
 
         The protocol can be an actual class or interface, or the *name* of a
         class or interface in the form '<module_name>.<class_name>'.
@@ -76,7 +76,7 @@ class or interface in the form '<module_name>.<class_name>'.
         """
 
     def get_service_properties(self, service_id):
-        """ Return the dictionary of properties associated with a service.
+        """Return the dictionary of properties associated with a service.
 
         If no such service exists a 'ValueError' exception is raised.
 
@@ -86,7 +86,7 @@ def get_service_properties(self, service_id):
         """
 
     def register_service(self, protocol, obj, properties=None):
-        """ Register a service.
+        """Register a service.
 
         The protocol can be an actual class or interface, or the *name* of a
         class or interface in the form::
@@ -111,14 +111,14 @@ class or interface in the form::
         """
 
     def set_service_properties(self, service_id, properties):
-        """ Set the dictionary of properties associated with a service.
+        """Set the dictionary of properties associated with a service.
 
         If no such service exists a 'ValueError' exception is raised.
 
         """
 
     def unregister_service(self, service_id):
-        """ Unregister a service.
+        """Unregister a service.
 
         If no such service exists a 'ValueError' exception is raised.
 
diff --git a/envisage/i_service_user.py b/envisage/i_service_user.py
index ef6028775..118d66557 100644
--- a/envisage/i_service_user.py
+++ b/envisage/i_service_user.py
@@ -18,7 +18,7 @@
 
 
 class IServiceUser(Interface):
-    """ The interface for objects using the 'Service' trait type. """
+    """The interface for objects using the 'Service' trait type."""
 
     # The service registry that the object's services are stored in.
     service_registry = Instance(IServiceRegistry)
diff --git a/envisage/ids.py b/envisage/ids.py
index 57ffa6e25..63c5eca4d 100644
--- a/envisage/ids.py
+++ b/envisage/ids.py
@@ -20,33 +20,33 @@
 
 #: Extension Point to contribute preference files, defined on the
 #: ``CorePlugin``.
-PREFERENCES = 'envisage.preferences'
+PREFERENCES = "envisage.preferences"
 
 #: Extension Point to contribute ``ServiceOffer`` s, defined on the
 #: ``CorePlugin``.
-SERVICE_OFFERS = 'envisage.service_offers'
+SERVICE_OFFERS = "envisage.service_offers"
 
 # NOTE : The other PythonShellPlugin defines extension points with the same ID.
 #: Extension Point to contribute name/value pairs that will be bound to the
 #: ``PythonShell``, defined on the ``PythonShellPlugin``.
-BINDINGS = 'envisage.plugins.python_shell.bindings'
+BINDINGS = "envisage.plugins.python_shell.bindings"
 
 #: Extension Point to contribute commands that will be executed in the
 #: ``PythonShell``, defined on the ``PythonShellPlugin``.
-COMMANDS = 'envisage.plugins.python_shell.commands'
+COMMANDS = "envisage.plugins.python_shell.commands"
 
 #: Extension Point to contribute preferences categories, defined on the
 #: ``TasksPlugin``.
-PREFERENCES_CATEGORIES = 'envisage.ui.tasks.preferences_categories'
+PREFERENCES_CATEGORIES = "envisage.ui.tasks.preferences_categories"
 
 #: Extension Point to contribute preference panes, defined on the
 #: ``TasksPlugin``.
-PREFERENCES_PANES = 'envisage.ui.tasks.preferences_panes'
+PREFERENCES_PANES = "envisage.ui.tasks.preferences_panes"
 
 #: Extension Point to contribute task factories, defined on the
 #: ``TasksPlugin``.
-TASKS = 'envisage.ui.tasks.tasks'
+TASKS = "envisage.ui.tasks.tasks"
 
 #: Extension Point to contribute task extensions, defined on the
 #: ``TasksPlugin``.
-TASK_EXTENSIONS = 'envisage.ui.tasks.task_extensions'
+TASK_EXTENSIONS = "envisage.ui.tasks.task_extensions"
diff --git a/envisage/import_manager.py b/envisage/import_manager.py
index 8c3af62af..56a02d73d 100644
--- a/envisage/import_manager.py
+++ b/envisage/import_manager.py
@@ -20,7 +20,7 @@
 
 @provides(IImportManager)
 class ImportManager(HasTraits):
-    """ The default import manager implementation.
+    """The default import manager implementation.
 
     Its just a guess, but I think using an import manager to do all imports
     will make debugging easier (as opposed to just letting imports happen from
@@ -33,7 +33,7 @@ class ImportManager(HasTraits):
     ###########################################################################
 
     def import_symbol(self, symbol_path):
-        """ Import the symbol defined by the specified symbol path. """
+        """Import the symbol defined by the specified symbol path."""
 
         if ":" in symbol_path:
             module_name, symbol_name = symbol_path.split(":")
diff --git a/envisage/package_plugin_manager.py b/envisage/package_plugin_manager.py
index dff79b5b1..0de01d8b1 100644
--- a/envisage/package_plugin_manager.py
+++ b/envisage/package_plugin_manager.py
@@ -19,12 +19,11 @@
 
 from .plugin_manager import PluginManager
 
-
 logger = logging.getLogger(__name__)
 
 
 class PackagePluginManager(PluginManager):
-    """ A plugin manager that finds plugins in packages on the 'plugin_path'.
+    """A plugin manager that finds plugins in packages on the 'plugin_path'.
 
     All items in 'plugin_path' are directory names and they are all added to
     'sys.path' (if not already present). Each directory is then searched for
@@ -68,7 +67,7 @@ def _update_path_and_reset_plugins(self, obj, trait_name, removed, added):
     #### Protected 'PluginManager' protocol ###################################
 
     def __plugins_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         plugins = [
             plugin
@@ -83,7 +82,7 @@ def __plugins_default(self):
     #### Private protocol #####################################################
 
     def _get_plugins_module(self, package_name):
-        """ Import 'plugins.py' from the package with the given name.
+        """Import 'plugins.py' from the package with the given name.
 
         If the package does not exist, or does not contain 'plugins.py' then
         return None.
@@ -102,7 +101,7 @@ def _get_plugins_module(self, package_name):
 
     # smell: Looooong and ugly!
     def _harvest_plugins_in_package(self, package_name, package_dirname):
-        """ Harvest plugins found in the given package. """
+        """Harvest plugins found in the given package."""
 
         # If the package contains a 'plugins.py' module, then we import it and
         # look for a callable 'get_plugins' that takes no arguments and returns
@@ -136,7 +135,7 @@ def _harvest_plugins_in_package(self, package_name, package_dirname):
         return plugins
 
     def _harvest_plugins_in_packages(self):
-        """ Harvest plugins found in packages on the plugin path. """
+        """Harvest plugins found in packages on the plugin path."""
 
         plugins = []
         for dirname in self.plugin_path:
@@ -151,7 +150,7 @@ def _harvest_plugins_in_packages(self):
         return plugins
 
     def _update_sys_dot_path(self, removed, added):
-        """ Add/remove the given entries from sys.path. """
+        """Add/remove the given entries from sys.path."""
 
         for dirname in removed:
             if dirname in sys.path:
diff --git a/envisage/plugin.py b/envisage/plugin.py
index 832b5fd40..ae68a240b 100644
--- a/envisage/plugin.py
+++ b/envisage/plugin.py
@@ -15,7 +15,7 @@
 from os.path import exists, join
 
 # Enthought library imports.
-from traits.api import Instance, List, Property, Str, provides
+from traits.api import Instance, List, Property, provides, Str
 from traits.util.camel_case import camel_case_to_words
 
 # Local imports.
@@ -36,7 +36,7 @@
 
 @provides(IPlugin, IExtensionPointUser, IServiceUser)
 class Plugin(ExtensionProvider):
-    """ The default implementation of the 'IPlugin' interface.
+    """The default implementation of the 'IPlugin' interface.
 
     This class is intended to be subclassed for each plugin that you create.
 
@@ -92,7 +92,7 @@ class Plugin(ExtensionProvider):
     ###########################################################################
 
     def _get_extension_registry(self):
-        """ Trait property getter. """
+        """Trait property getter."""
 
         return self.application
 
@@ -101,7 +101,7 @@ def _get_extension_registry(self):
     ###########################################################################
 
     def _get_service_registry(self):
-        """ Trait property getter. """
+        """Trait property getter."""
 
         return self.application
 
@@ -110,7 +110,7 @@ def _get_service_registry(self):
     ###########################################################################
 
     def get_extension_points(self):
-        """ Return the extension points offered by the provider. """
+        """Return the extension points offered by the provider."""
 
         extension_points = [
             trait.trait_type
@@ -120,7 +120,7 @@ def get_extension_points(self):
         return extension_points
 
     def get_extensions(self, extension_point_id):
-        """ Return the provider's extensions to an extension point. """
+        """Return the provider's extensions to an extension point."""
 
         # Each class can have at most *one* trait that contributes to a
         # particular extension point.
@@ -148,7 +148,7 @@ def get_extensions(self, extension_point_id):
     #### Trait initializers ###################################################
 
     def _home_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # Each plugin gets a sub-directory of a 'plugins' directory in
         # 'application.home'.
@@ -166,23 +166,25 @@ def _home_default(self):
         return home_dir
 
     def _id_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         id = "%s.%s" % (type(self).__module__, type(self).__name__)
         logger.warning(
             "plugin {} has no Id - using <{}>".format(
-                object.__repr__(self), id)
+                object.__repr__(self), id
+            )
         )
 
         return id
 
     def _name_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         name = camel_case_to_words(type(self).__name__)
         logger.warning(
             "plugin {} has no name - using <{}>".format(
-                object.__repr__(self), name)
+                object.__repr__(self), name
+            )
         )
 
         return name
@@ -190,7 +192,7 @@ def _name_default(self):
     #### Methods ##############################################################
 
     def start(self):
-        """ Start the plugin.
+        """Start the plugin.
 
         This method will *always* be empty so that you never have to call
         'super().start()' if you provide an implementation in a
@@ -204,7 +206,7 @@ def start(self):
         pass
 
     def stop(self):
-        """ Stop the plugin.
+        """Stop the plugin.
 
         This method will *always* be empty so that you never have to call
         'super().stop()' if you provide an implementation in a
@@ -222,7 +224,7 @@ def stop(self):
     ###########################################################################
 
     def connect_extension_point_traits(self):
-        """ Connect all of the plugin's extension points.
+        """Connect all of the plugin's extension points.
 
         This means that the plugin will be notified if and when contributions
         are add or removed.
@@ -232,12 +234,12 @@ def connect_extension_point_traits(self):
         ExtensionPoint.connect_extension_point_traits(self)
 
     def disconnect_extension_point_traits(self):
-        """ Disconnect all of the plugin's extension points."""
+        """Disconnect all of the plugin's extension points."""
 
         ExtensionPoint.disconnect_extension_point_traits(self)
 
     def register_services(self):
-        """ Register the services offered by the plugin. """
+        """Register the services offered by the plugin."""
 
         for trait_name, trait in self.traits(service=True).items():
             logger.warning(
@@ -256,7 +258,7 @@ def register_services(self):
             self._service_ids.append(service_id)
 
     def unregister_services(self):
-        """ Unregister any service offered by the plugin. """
+        """Unregister any service offered by the plugin."""
 
         # Unregister the services in the reverse order that we registered
         # them.
@@ -282,7 +284,7 @@ def unregister_services(self):
     #### Trait change handlers ################################################
 
     def _anytrait_changed(self, trait_name, old, new):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         # Ignore the '_items' part of the trait name (if it is there!), and get
         # the actual trait.
@@ -310,7 +312,7 @@ def _anytrait_changed(self, trait_name, old, new):
     #### Methods ##############################################################
 
     def _create_multiple_traits_exception(self, extension_point_id):
-        """ Create the exception raised when multiple traits are found. """
+        """Create the exception raised when multiple traits are found."""
 
         exception = ValueError(
             "multiple traits for extension point <%s> in plugin <%s>"
@@ -320,7 +322,7 @@ def _create_multiple_traits_exception(self, extension_point_id):
         return exception
 
     def _get_extensions_from_trait(self, trait_name):
-        """ Return the extensions contributed via the specified trait. """
+        """Return the extensions contributed via the specified trait."""
 
         try:
             extensions = getattr(self, trait_name)
@@ -334,7 +336,7 @@ def _get_extensions_from_trait(self, trait_name):
         return extensions
 
     def _get_service_protocol(self, trait):
-        """ Determine the protocol to register a service trait with. """
+        """Determine the protocol to register a service trait with."""
 
         # If a specific protocol was specified then use it.
         if trait.service_protocol is not None:
@@ -354,7 +356,7 @@ def _get_service_protocol(self, trait):
         return protocol
 
     def _register_service_factory(self, trait_name, trait):
-        """ Register a service factory for the specified trait. """
+        """Register a service factory for the specified trait."""
 
         # Determine the protocol that the service should be registered with.
         protocol = self._get_service_protocol(trait)
@@ -364,7 +366,7 @@ def _register_service_factory(self, trait_name, trait):
         # (this could obviously be a lambda function, but I thought it best to
         # be more explicit 8^).
         def factory(**properties):
-            """ A service factory. """
+            """A service factory."""
 
             return getattr(self, trait_name)
 
@@ -375,5 +377,5 @@ def factory(**properties):
     ###########################################################################
 
     def __repr__(self):
-        """ String representation of a Plugin object """
+        """String representation of a Plugin object"""
         return f"{type(self).__name__}(id={self.id!r}, name={self.name!r})"
diff --git a/envisage/plugin_activator.py b/envisage/plugin_activator.py
index 574fae403..4b9a280e5 100644
--- a/envisage/plugin_activator.py
+++ b/envisage/plugin_activator.py
@@ -19,14 +19,14 @@
 
 @provides(IPluginActivator)
 class PluginActivator(HasTraits):
-    """ The default plugin activator. """
+    """The default plugin activator."""
 
     ###########################################################################
     # 'IPluginActivator' interface.
     ###########################################################################
 
     def start_plugin(self, plugin):
-        """ Start the specified plugin. """
+        """Start the specified plugin."""
 
         # Connect all of the plugin's extension point traits so that the plugin
         # will be notified if and when contributions are added or removed.
@@ -39,7 +39,7 @@ def start_plugin(self, plugin):
         plugin.start()
 
     def stop_plugin(self, plugin):
-        """ Stop the specified plugin. """
+        """Stop the specified plugin."""
 
         # Plugin specific stop.
         plugin.stop()
diff --git a/envisage/plugin_event.py b/envisage/plugin_event.py
index 6e3f9379c..cbff3c3a7 100644
--- a/envisage/plugin_event.py
+++ b/envisage/plugin_event.py
@@ -15,7 +15,7 @@
 
 
 class PluginEvent(Vetoable):
-    """ A plugin event. """
+    """A plugin event."""
 
     # The plugin that the event is for.
     plugin = Instance("envisage.api.IPlugin")
diff --git a/envisage/plugin_extension_registry.py b/envisage/plugin_extension_registry.py
index 78761c0de..7adeed5be 100644
--- a/envisage/plugin_extension_registry.py
+++ b/envisage/plugin_extension_registry.py
@@ -19,7 +19,7 @@
 
 
 class PluginExtensionRegistry(ProviderExtensionRegistry):
-    """ An extension registry that uses plugins as extension providers.
+    """An extension registry that uses plugins as extension providers.
 
     The application's plugins are used as the registries providers so adding
     or removing a plugin affects the extension points and extensions etc.
@@ -39,7 +39,7 @@ class PluginExtensionRegistry(ProviderExtensionRegistry):
 
     @observe("plugin_manager")
     def _update_providers(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
         old, new = event.old, event.new
 
         # In practise I can't see why you would ever want (or need) to change
@@ -55,12 +55,12 @@ def _update_providers(self, event):
 
     @on_trait_change("plugin_manager:plugin_added")
     def _on_plugin_added(self, obj, trait_name, old, event):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         self.add_provider(event.plugin)
 
     @on_trait_change("plugin_manager:plugin_removed")
     def _on_plugin_removed(self, obj, trait_name, old, event):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         self.remove_provider(event.plugin)
diff --git a/envisage/plugin_manager.py b/envisage/plugin_manager.py
index d7c1e9cf9..882149e62 100644
--- a/envisage/plugin_manager.py
+++ b/envisage/plugin_manager.py
@@ -10,9 +10,9 @@
 """ A simple plugin manager implementation. """
 
 
-from fnmatch import fnmatch
 import logging
 import warnings
+from fnmatch import fnmatch
 
 from traits.api import Event, HasTraits, Instance, List, observe, provides, Str
 
@@ -21,13 +21,12 @@
 from .i_plugin_manager import IPluginManager
 from .plugin_event import PluginEvent
 
-
 logger = logging.getLogger(__name__)
 
 
 @provides(IPluginManager)
 class PluginManager(HasTraits):
-    """ A simple plugin manager implementation.
+    """A simple plugin manager implementation.
 
     This implementation manages an explicit collection of plugin instances,
     e.g::
@@ -54,7 +53,7 @@ class PluginManager(HasTraits):
 
     @observe("application")
     def _set_new_application_on_all_plugins(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         self._update_application_on_plugins([], self._plugins)
 
@@ -74,7 +73,7 @@ def _set_new_application_on_all_plugins(self, event):
     #### 'object' protocol ####################################################
 
     def __init__(self, plugins=None, **traits):
-        """ Constructor.
+        """Constructor.
 
         We allow the caller to specify an initial list of plugins, but the
         list itself is not part of the public API. To add and remove plugins
@@ -98,7 +97,7 @@ def __init__(self, plugins=None, **traits):
             self._plugins = plugins
 
     def __iter__(self):
-        """ Return an iterator over the manager's plugins. """
+        """Return an iterator over the manager's plugins."""
 
         plugins = [
             plugin
@@ -111,13 +110,13 @@ def __iter__(self):
     #### 'IPluginManager' protocol ############################################
 
     def add_plugin(self, plugin):
-        """ Add a plugin to the manager. """
+        """Add a plugin to the manager."""
 
         self._plugins.append(plugin)
         self.plugin_added = PluginEvent(plugin=plugin)
 
     def get_plugin(self, plugin_id):
-        """ Return the plugin with the specified Id. """
+        """Return the plugin with the specified Id."""
 
         for plugin in self._plugins:
             if plugin_id == plugin.id:
@@ -132,19 +131,19 @@ def get_plugin(self, plugin_id):
         return plugin
 
     def remove_plugin(self, plugin):
-        """ Remove a plugin from the manager. """
+        """Remove a plugin from the manager."""
 
         self._plugins.remove(plugin)
         self.plugin_removed = PluginEvent(plugin=plugin)
 
     def start(self):
-        """ Start the plugin manager. """
+        """Start the plugin manager."""
 
         for plugin in self._plugins:
             self.start_plugin(plugin)
 
     def start_plugin(self, plugin=None, plugin_id=None):
-        """ Start the specified plugin. """
+        """Start the specified plugin."""
 
         plugin = plugin or self.get_plugin(plugin_id)
         if plugin is not None:
@@ -156,7 +155,7 @@ def start_plugin(self, plugin=None, plugin_id=None):
             raise ValueError("no such plugin %s" % plugin_id)
 
     def stop(self):
-        """ Stop the plugin manager. """
+        """Stop the plugin manager."""
 
         # We stop the plugins in the reverse order that they were started.
         stop_order = self._plugins[:]
@@ -166,7 +165,7 @@ def stop(self):
             self.stop_plugin(plugin)
 
     def stop_plugin(self, plugin=None, plugin_id=None):
-        """ Stop the specified plugin. """
+        """Stop the specified plugin."""
 
         plugin = plugin or self.get_plugin(plugin_id)
         if plugin is not None:
@@ -184,18 +183,18 @@ def stop_plugin(self, plugin=None, plugin_id=None):
 
     @observe("_plugins")
     def _update_application_on_all_plugins(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
         old, new = event.old, event.new
         self._update_application_on_plugins(old, new)
 
     @observe("_plugins:items")
     def _update_application_on_changed_plugins(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         self._update_application_on_plugins(event.removed, event.added)
 
     def _include_plugin(self, plugin_id):
-        """ Return True if the plugin should be included.
+        """Return True if the plugin should be included.
 
         This is just shorthand for:-
 
@@ -211,7 +210,7 @@ def _include_plugin(self, plugin_id):
     #### Private protocol #####################################################
 
     def _is_excluded(self, plugin_id):
-        """ Return True if the plugin Id is excluded.
+        """Return True if the plugin Id is excluded.
 
         If no 'exclude' patterns are specified then this method returns False
         for all plugin Ids.
@@ -228,7 +227,7 @@ def _is_excluded(self, plugin_id):
         return False
 
     def _is_included(self, plugin_id):
-        """ Return True if the plugin Id is included.
+        """Return True if the plugin Id is included.
 
         If no 'include' patterns are specified then this method returns True
         for all plugin Ids.
@@ -245,7 +244,7 @@ def _is_included(self, plugin_id):
         return False
 
     def _update_application_on_plugins(self, removed, added):
-        """ Update the 'application' trait of plugins added/removed. """
+        """Update the 'application' trait of plugins added/removed."""
 
         for plugin in removed:
             plugin.application = None
diff --git a/envisage/plugins/event_manager/plugin.py b/envisage/plugins/event_manager/plugin.py
index acd4e22ff..d7ac3169e 100644
--- a/envisage/plugins/event_manager/plugin.py
+++ b/envisage/plugins/event_manager/plugin.py
@@ -15,13 +15,14 @@
 of the application to the created event manager.
 """
 
+from traits.api import List
+
 # Enthought library imports.
 from envisage.api import Plugin, ServiceOffer
-from traits.api import List
 
 
 class EventManagerPlugin(Plugin):
-    """ Plugin to add event manager to the application. """
+    """Plugin to add event manager to the application."""
 
     id = "envisage.event_manager"
 
@@ -32,6 +33,7 @@ def _service_offers_default(self):
         from encore.events.api import BaseEventManager, get_event_manager
 
         evt_mgr_service_offer = ServiceOffer(
-            protocol=BaseEventManager, factory=get_event_manager,
+            protocol=BaseEventManager,
+            factory=get_event_manager,
         )
         return [evt_mgr_service_offer]
diff --git a/envisage/plugins/python_shell/i_python_shell.py b/envisage/plugins/python_shell/i_python_shell.py
index 4e7b65c59..7296544b1 100644
--- a/envisage/plugins/python_shell/i_python_shell.py
+++ b/envisage/plugins/python_shell/i_python_shell.py
@@ -15,24 +15,16 @@
 
 
 class IPythonShell(Interface):
-    """ A simple interface for the Python shell. """
+    """A simple interface for the Python shell."""
 
     def bind(self, name, value):
-        """ Binds a name to a value in the interpreter's namespace.
-
-        """
+        """Binds a name to a value in the interpreter's namespace."""
 
     def execute_command(self, command, hidden=True):
-        """ Execute a command in the interpreter.
-
-        """
+        """Execute a command in the interpreter."""
 
     def execute_file(self, path, hidden=True):
-        """ Execute a file in the interpreter.
-
-        """
+        """Execute a file in the interpreter."""
 
     def lookup(self, name):
-        """ Returns the value bound to a name in the interpreter's namespace.
-
-        """
+        """Returns the value bound to a name in the interpreter's namespace."""
diff --git a/envisage/plugins/python_shell/python_shell_plugin.py b/envisage/plugins/python_shell/python_shell_plugin.py
index bdcd260d2..b80870c0c 100644
--- a/envisage/plugins/python_shell/python_shell_plugin.py
+++ b/envisage/plugins/python_shell/python_shell_plugin.py
@@ -10,13 +10,14 @@
 """ The interactive Python shell plugin. """
 
 
+from traits.api import Dict, List, Str
+
 # Enthought library imports.
 from envisage.api import ExtensionPoint, Plugin
-from traits.api import Dict, List, Str
 
 
 class PythonShellPlugin(Plugin):
-    """ The interactive Python shell plugin. """
+    """The interactive Python shell plugin."""
 
     # Extension point Ids.
     BINDINGS = "envisage.plugins.python_shell.bindings"
@@ -73,7 +74,7 @@ class PythonShellPlugin(Plugin):
     contributed_bindings = List(contributes_to=BINDINGS)
 
     def _contributed_bindings_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return [{"application": self.application}]
 
@@ -81,10 +82,10 @@ def _contributed_bindings_default(self):
     contributed_views = List(contributes_to=VIEWS)
 
     def _contributed_views_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # Local imports.
-        from .view.python_shell_view import PythonShellView
         from .view.namespace_view import NamespaceView
+        from .view.python_shell_view import PythonShellView
 
         return [PythonShellView, NamespaceView]
diff --git a/envisage/plugins/python_shell/view/namespace_view.py b/envisage/plugins/python_shell/view/namespace_view.py
index 038180197..58013dfb7 100644
--- a/envisage/plugins/python_shell/view/namespace_view.py
+++ b/envisage/plugins/python_shell/view/namespace_view.py
@@ -11,31 +11,30 @@
 
 # Enthought library imports.
 
-from envisage.plugins.python_shell.api import IPythonShell
-from envisage.plugins.python_shell.view.python_shell_view import (
-    PythonShellView,
-)
-
 from pyface.workbench.api import View
-
 from traits.api import (
+    cached_property,
+    DelegatesTo,
     HasTraits,
-    Str,
-    Property,
-    List,
     Instance,
-    DelegatesTo,
-    cached_property,
+    List,
+    Property,
+    Str,
 )
-
 from traitsui.api import Item, TableEditor, VGroup
 from traitsui.api import View as TraitsView
 from traitsui.table_column import ObjectColumn
-from traitsui.table_filter import RuleTableFilter
-from traitsui.table_filter import MenuFilterTemplate
-from traitsui.table_filter import EvalFilterTemplate
-from traitsui.table_filter import RuleFilterTemplate
+from traitsui.table_filter import (
+    EvalFilterTemplate,
+    MenuFilterTemplate,
+    RuleFilterTemplate,
+    RuleTableFilter,
+)
 
+from envisage.plugins.python_shell.api import IPythonShell
+from envisage.plugins.python_shell.view.python_shell_view import (
+    PythonShellView,
+)
 
 # Table editor definition:
 filters = [EvalFilterTemplate, MenuFilterTemplate, RuleFilterTemplate]
@@ -82,7 +81,7 @@ def module_to_str(obj):
 
 
 class NamespaceView(View):
-    """ A view containing the contents of the Python shell namespace. """
+    """A view containing the contents of the Python shell namespace."""
 
     #### 'IView' interface ####################################################
 
@@ -127,7 +126,7 @@ class NamespaceView(View):
     ###########################################################################
 
     def create_control(self, parent):
-        """ Creates the toolkit-specific control that represents the view.
+        """Creates the toolkit-specific control that represents the view.
 
         'parent' is the toolkit-specific control that is the view's parent.
 
@@ -149,7 +148,7 @@ def create_control(self, parent):
 
     @cached_property
     def _get_bindings(self):
-        """ Property getter. """
+        """Property getter."""
 
         if self.shell_view is None:
             return []
diff --git a/envisage/plugins/python_shell/view/python_shell_view.py b/envisage/plugins/python_shell/view/python_shell_view.py
index 40248fc83..260a3dc1d 100644
--- a/envisage/plugins/python_shell/view/python_shell_view.py
+++ b/envisage/plugins/python_shell/view/python_shell_view.py
@@ -14,21 +14,20 @@
 import logging
 import sys
 
-# Enthought library imports.
-from envisage.api import IExtensionRegistry
-from envisage.api import ExtensionPoint
-from envisage.plugins.python_shell.api import IPythonShell
 from pyface.api import PythonShell
 from pyface.workbench.api import View
 from traits.api import Any, Dict, Event, Instance, Property, provides, Str
 
+# Enthought library imports.
+from envisage.api import ExtensionPoint, IExtensionRegistry
+from envisage.plugins.python_shell.api import IPythonShell
+
 # Setup a logger for this module.
 logger = logging.getLogger(__name__)
 
 
 class PseudoFile(object):
-    """ Simulates a normal File object.
-    """
+    """Simulates a normal File object."""
 
     def __init__(self, write):
         self.write = write
@@ -49,7 +48,7 @@ def isatty(self):
 
 @provides(IPythonShell)
 class PythonShellView(View):
-    """ A view containing an interactive Python shell. """
+    """A view containing an interactive Python shell."""
 
     #### 'IView' interface ####################################################
 
@@ -95,7 +94,7 @@ class PythonShellView(View):
     ###########################################################################
 
     def _get_extension_registry(self):
-        """ Trait property getter. """
+        """Trait property getter."""
 
         return self.window.application
 
@@ -104,7 +103,7 @@ def _get_extension_registry(self):
     ###########################################################################
 
     def create_control(self, parent):
-        """ Creates the toolkit-specific control that represents the view. """
+        """Creates the toolkit-specific control that represents the view."""
 
         self.shell = shell = PythonShell(parent)
         shell.on_trait_change(self._on_key_pressed, "key_pressed")
@@ -139,9 +138,7 @@ def create_control(self, parent):
         return self.shell.control
 
     def destroy_control(self):
-        """ Destroys the toolkit-specific control that represents the view.
-
-        """
+        """Destroys the toolkit-specific control that represents the view."""
 
         super().destroy_control()
 
@@ -161,36 +158,34 @@ def destroy_control(self):
     #### Properties ###########################################################
 
     def _get_namespace(self):
-        """ Property getter. """
+        """Property getter."""
 
         return self.shell.interpreter().locals
 
     def _get_names(self):
-        """ Property getter. """
+        """Property getter."""
 
         return list(self.shell.interpreter().locals.keys())
 
     #### Methods ##############################################################
 
     def bind(self, name, value):
-        """ Binds a name to a value in the interpreter's namespace. """
+        """Binds a name to a value in the interpreter's namespace."""
 
         self.shell.bind(name, value)
 
     def execute_command(self, command, hidden=True):
-        """ Execute a command in the interpreter. """
+        """Execute a command in the interpreter."""
 
         return self.shell.execute_command(command, hidden)
 
     def execute_file(self, path, hidden=True):
-        """ Execute a command in the interpreter. """
+        """Execute a command in the interpreter."""
 
         return self.shell.execute_file(path, hidden)
 
     def lookup(self, name):
-        """ Returns the value bound to a name in the interpreter's namespace.
-
-        """
+        """Returns the value bound to a name in the interpreter's namespace."""
 
         return self.shell.interpreter().locals[name]
 
@@ -199,14 +194,14 @@ def lookup(self, name):
     ###########################################################################
 
     def _write_stdout(self, text):
-        """ Handles text written to stdout. """
+        """Handles text written to stdout."""
 
         self.stdout_text = text
 
     #### Trait change handlers ################################################
 
     def _on_command_executed(self, shell):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         if self.control is not None:
             # Get the set of tuples of names and types in the current
@@ -225,7 +220,7 @@ def _on_command_executed(self, shell):
                 self.trait_property_changed("names", [], self.names)
 
     def _on_key_pressed(self, event):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         if event.alt_down and event.key_code == 317:
             zoom = self.shell.control.GetZoom()
@@ -238,6 +233,6 @@ def _on_key_pressed(self, event):
                 self.shell.control.SetZoom(zoom - 1)
 
     def _on_write_stdout(self, text):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         self.shell.control.write(text)
diff --git a/envisage/plugins/tasks/python_shell_plugin.py b/envisage/plugins/tasks/python_shell_plugin.py
index ee9271c48..ff611f034 100644
--- a/envisage/plugins/tasks/python_shell_plugin.py
+++ b/envisage/plugins/tasks/python_shell_plugin.py
@@ -17,10 +17,12 @@
 # Standard library imports.
 import logging
 
-# Enthought library imports.
-from traits.api import Str, List, Dict, Instance, Property
 from pyface.tasks.contrib.python_shell import PythonShellTask
-from envisage.api import Plugin, ExtensionPoint, IExtensionRegistry
+
+# Enthought library imports.
+from traits.api import Dict, Instance, List, Property, Str
+
+from envisage.api import ExtensionPoint, IExtensionRegistry, Plugin
 from envisage.ui.tasks.api import TaskFactory
 
 logger = logging.getLogger()
@@ -30,7 +32,7 @@
 
 
 class EnvisagePythonShellTask(PythonShellTask):
-    """ Subclass of PythonShellTask that gets its bindings and commands from
+    """Subclass of PythonShellTask that gets its bindings and commands from
     an Envisage ExtensionPoint
     """
 
@@ -54,8 +56,7 @@ def _get_extension_registry(self):
 
 
 class PythonShellPlugin(Plugin):
-    """ A tasks plugin to display a simple Python shell to the user.
-    """
+    """A tasks plugin to display a simple Python shell to the user."""
 
     # Extension point IDs.
     BINDINGS = BINDINGS
@@ -116,7 +117,8 @@ def start(self):
         logger.debug("started python shell plugin")
 
     def _contributed_bindings_default(self):
-        """ By default, expose the Envisage application object to the namespace
+        """
+        By default, expose the Envisage application object to the namespace
         """
         return [{"application": self.application}]
 
diff --git a/envisage/plugins/text_editor/actions.py b/envisage/plugins/text_editor/actions.py
index 1c8b77759..bd043d475 100644
--- a/envisage/plugins/text_editor/actions.py
+++ b/envisage/plugins/text_editor/actions.py
@@ -10,8 +10,8 @@
 import logging
 
 from apptools.io.api import File
-from pyface.api import FileDialog, OK
 from pyface.action.api import Action
+from pyface.api import FileDialog, OK
 from traits.api import Any
 
 from .editor.text_editor import TextEditor
@@ -20,8 +20,7 @@
 
 
 class NewFileAction(Action):
-    """ Open a new file in the text editor.
-    """
+    """Open a new file in the text editor."""
 
     tooltip = "Create a new file for editing"
     description = "Create a new file for editing"
@@ -37,8 +36,7 @@ def perform(self, event=None):
 
 
 class OpenFileAction(Action):
-    """ Open an existing file in the text editor.
-    """
+    """Open an existing file in the text editor."""
 
     tooltip = "Open a file for editing"
     description = "Open a file for editing"
diff --git a/envisage/plugins/text_editor/api.py b/envisage/plugins/text_editor/api.py
index f18948835..da7a1bf36 100644
--- a/envisage/plugins/text_editor/api.py
+++ b/envisage/plugins/text_editor/api.py
@@ -7,5 +7,5 @@
 # is also available online at http://www.enthought.com/licenses/BSD.txt
 #
 # Thanks for using Enthought open source!
-from .text_editor_action_set import TextEditorActionSet
 from .editor.text_editor import TextEditor
+from .text_editor_action_set import TextEditorActionSet
diff --git a/envisage/plugins/text_editor/editor/text_editor.py b/envisage/plugins/text_editor/editor/text_editor.py
index f25f54d33..a063bbd8f 100644
--- a/envisage/plugins/text_editor/editor/text_editor.py
+++ b/envisage/plugins/text_editor/editor/text_editor.py
@@ -13,9 +13,10 @@
 # Standard library imports.
 from os.path import basename
 
+from pyface.api import CANCEL, FileDialog
+
 # Enthought library imports.
 from pyface.workbench.api import TraitsUIEditor
-from pyface.api import FileDialog, CANCEL
 from traits.api import Code, Instance, observe
 from traitsui.api import CodeEditor, Group, Item, View
 from traitsui.key_bindings import KeyBinding, KeyBindings
@@ -26,7 +27,7 @@
 
 
 def _id_generator():
-    """ A generator that returns the next number for untitled files. """
+    """A generator that returns the next number for untitled files."""
 
     i = 1
     while True:
@@ -38,7 +39,7 @@ def _id_generator():
 
 
 class TextEditor(TraitsUIEditor):
-    """ A text editor. """
+    """A text editor."""
 
     #### 'TextEditor' interface ###############################################
 
@@ -53,7 +54,7 @@ class TextEditor(TraitsUIEditor):
     ###########################################################################
 
     def save(self):
-        """ Saves the text to disk. """
+        """Saves the text to disk."""
 
         # If the file has not yet been saved then prompt for the file name.
         if len(self.obj.path) == 0:
@@ -67,7 +68,7 @@ def save(self):
             self.dirty = False
 
     def save_as(self):
-        """ Saves the text to disk after prompting for the file name. """
+        """Saves the text to disk after prompting for the file name."""
 
         dialog = FileDialog(
             parent=self.window.control,
@@ -91,7 +92,7 @@ def save_as(self):
     ###########################################################################
 
     def create_ui(self, parent):
-        """ Creates the traits UI that represents the editor. """
+        """Creates the traits UI that represents the editor."""
 
         ui = self.edit_traits(
             parent=parent, view=self._create_traits_ui_view(), kind="subpanel"
@@ -104,7 +105,7 @@ def create_ui(self, parent):
     ###########################################################################
 
     def run(self):
-        """ Runs the file as Python. """
+        """Runs the file as Python."""
 
         # The file must be saved first!
         self.save()
@@ -121,7 +122,7 @@ def run(self):
                 )
 
     def select_line(self, lineno):
-        """ Selects the specified line. """
+        """Selects the specified line."""
 
         self.ui.info.text.selected_line = lineno
 
@@ -132,7 +133,7 @@ def select_line(self, lineno):
     #### Trait initializers ###################################################
 
     def _key_bindings_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         key_bindings = KeyBindings(
             KeyBinding(
@@ -153,7 +154,7 @@ def _key_bindings_default(self):
 
     @observe("obj")
     def _handle_update_to_object(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
         new = event.new
         # The path will be the empty string if we are editing a file that has
         # not yet been saved.
@@ -170,14 +171,14 @@ def _handle_update_to_object(self, event):
 
     @observe("text")
     def _update_dirty(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         if self.traits_inited():
             self.dirty = True
 
     @observe("dirty")
     def _update_name(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
         dirty = event.new
         if len(self.obj.path) > 0:
             if dirty:
@@ -189,7 +190,7 @@ def _update_name(self, event):
     #### Methods ##############################################################
 
     def _create_traits_ui_view(self):
-        """ Create the traits UI view used by the editor.
+        """Create the traits UI view used by the editor.
 
         fixme: We create the view dynamically to allow the key bindings to be
         created dynamically (we don't use this just yet, but obviously plugins
@@ -216,7 +217,7 @@ def _create_traits_ui_view(self):
         return view
 
     def _get_unique_id(self, prefix="Untitled "):
-        """ Return a unique id for a new file. """
+        """Return a unique id for a new file."""
 
         id = prefix + str(next(_id_generator))
         while self.window.get_editor_by_id(id) is not None:
diff --git a/envisage/plugins/text_editor/editor/text_editor_handler.py b/envisage/plugins/text_editor/editor/text_editor_handler.py
index 6844f1f27..93bc04bb9 100644
--- a/envisage/plugins/text_editor/editor/text_editor_handler.py
+++ b/envisage/plugins/text_editor/editor/text_editor_handler.py
@@ -15,7 +15,7 @@
 
 
 class TextEditorHandler(Handler):
-    """ The traits UI handler for the text editor. """
+    """The traits UI handler for the text editor."""
 
     ###########################################################################
     # 'TextEditorHandler' interface.
@@ -25,11 +25,11 @@ class TextEditorHandler(Handler):
     # dynamically! Plugins will want to add bindings to the editor to bind
     # a key to an action.
     def run(self, info):
-        """ Run the text as Python code. """
+        """Run the text as Python code."""
 
         info.object.run()
 
     def save(self, info):
-        """ Save the text to disk. """
+        """Save the text to disk."""
 
         info.object.save()
diff --git a/envisage/plugins/text_editor/text_editor_action_set.py b/envisage/plugins/text_editor/text_editor_action_set.py
index a921868e1..358f9cdd6 100644
--- a/envisage/plugins/text_editor/text_editor_action_set.py
+++ b/envisage/plugins/text_editor/text_editor_action_set.py
@@ -12,8 +12,7 @@
 
 
 class TextEditorActionSet(ActionSet):
-    """ The default action set for the Text Editor plugin.
-    """
+    """The default action set for the Text Editor plugin."""
 
     groups = [
         Group(id="TextFileGroup", path="MenuBar/File", before="ExitGroup")
diff --git a/envisage/plugins/text_editor/text_editor_plugin.py b/envisage/plugins/text_editor/text_editor_plugin.py
index dae5835a9..0648f6853 100644
--- a/envisage/plugins/text_editor/text_editor_plugin.py
+++ b/envisage/plugins/text_editor/text_editor_plugin.py
@@ -13,8 +13,8 @@
 
 # Enthought library imports.
 from traits.api import List
-from envisage.api import Plugin
 
+from envisage.api import Plugin
 
 # The plugin's globally unique identifier (also used as the prefix for all
 # identifiers defined in this module).
@@ -22,8 +22,7 @@
 
 
 class TextEditorPlugin(Plugin):
-    """ Text Editor plugin for the Workbench UI.
-    """
+    """Text Editor plugin for the Workbench UI."""
 
     name = "Text Editor plugin"
 
diff --git a/envisage/provider_extension_registry.py b/envisage/provider_extension_registry.py
index 855f5317e..cd16f7457 100644
--- a/envisage/provider_extension_registry.py
+++ b/envisage/provider_extension_registry.py
@@ -14,21 +14,20 @@
 import logging
 
 # Enthought library imports.
-from traits.api import List, provides, on_trait_change
+from traits.api import List, on_trait_change, provides
 
 # Local imports.
 from .extension_registry import ExtensionRegistry
 from .i_extension_provider import IExtensionProvider
 from .i_provider_extension_registry import IProviderExtensionRegistry
 
-
 # Logging.
 logger = logging.getLogger(__name__)
 
 
 @provides(IProviderExtensionRegistry)
 class ProviderExtensionRegistry(ExtensionRegistry):
-    """ An extension registry implementation with multiple providers. """
+    """An extension registry implementation with multiple providers."""
 
     #### Protected 'ProviderExtensionRegistry' interface ######################
 
@@ -40,7 +39,7 @@ class ProviderExtensionRegistry(ExtensionRegistry):
     ###########################################################################
 
     def set_extensions(self, extension_point_id, extensions):
-        """ Set the extensions to an extension point. """
+        """Set the extensions to an extension point."""
 
         raise TypeError("extension points cannot be set")
 
@@ -49,7 +48,7 @@ def set_extensions(self, extension_point_id, extensions):
     ###########################################################################
 
     def add_provider(self, provider):
-        """ Add an extension provider. """
+        """Add an extension provider."""
 
         events = self._add_provider(provider)
 
@@ -57,12 +56,12 @@ def add_provider(self, provider):
             self._call_listeners(refs, extension_point_id, added, [], index)
 
     def get_providers(self):
-        """ Return all of the providers in the registry. """
+        """Return all of the providers in the registry."""
 
         return self._providers[:]
 
     def remove_provider(self, provider):
-        """ Remove an extension provider.
+        """Remove an extension provider.
 
         Raise a 'ValueError' if the provider is not in the registry.
 
@@ -78,7 +77,7 @@ def remove_provider(self, provider):
     ###########################################################################
 
     def _get_extensions(self, extension_point_id):
-        """ Return the extensions for the given extension point. """
+        """Return the extensions for the given extension point."""
 
         # If we don't know about the extension point then it sure ain't got
         # any extensions!
@@ -119,7 +118,7 @@ def _get_extensions(self, extension_point_id):
     ###########################################################################
 
     def _add_provider(self, provider):
-        """ Add a new provider. """
+        """Add a new provider."""
 
         # Add the provider's extension points.
         self._add_provider_extension_points(provider)
@@ -133,7 +132,7 @@ def _add_provider(self, provider):
         return events
 
     def _add_provider_extensions(self, provider):
-        """ Add a provider's extensions to the registry. """
+        """Add a provider's extensions to the registry."""
 
         # Each provider can contribute to multiple extension points, so we
         # build up a dictionary of the 'ExtensionPointChanged' events that we
@@ -158,13 +157,13 @@ def _add_provider_extensions(self, provider):
         return events
 
     def _add_provider_extension_points(self, provider):
-        """ Add a provider's extension points to the registry. """
+        """Add a provider's extension points to the registry."""
 
         for extension_point in provider.get_extension_points():
             self._extension_points[extension_point.id] = extension_point
 
     def _remove_provider(self, provider):
-        """ Remove a provider. """
+        """Remove a provider."""
 
         # Remove the provider's extensions.
         events = self._remove_provider_extensions(provider)
@@ -178,7 +177,7 @@ def _remove_provider(self, provider):
         return events
 
     def _remove_provider_extensions(self, provider):
-        """ Remove a provider's extensions from the registry. """
+        """Remove a provider's extensions from the registry."""
 
         # Each provider can contribute to multiple extension points, so we
         # build up a dictionary of the 'ExtensionPointChanged' events that we
@@ -206,7 +205,7 @@ def _remove_provider_extensions(self, provider):
         return events
 
     def _remove_provider_extension_points(self, provider, events):
-        """ Remove a provider's extension points from the registry. """
+        """Remove a provider's extension points from the registry."""
 
         for extension_point in provider.get_extension_points():
             # Remove the extension point.
@@ -220,7 +219,7 @@ def _remove_provider_extension_points(self, provider, events):
 
     @on_trait_change("_providers:extension_point_changed")
     def _providers_extension_point_changed(self, obj, trait_name, old, event):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         logger.debug("provider <%s> extension point changed", obj)
 
@@ -270,7 +269,7 @@ def _providers_extension_point_changed(self, obj, trait_name, old, event):
     #### Methods ##############################################################
 
     def _initialize_extensions(self, extension_point_id):
-        """ Initialize the extensions to an extension point. """
+        """Initialize the extensions to an extension point."""
 
         # We store the extensions as a list of lists, with each inner list
         # containing the contributions from a single provider.
@@ -283,7 +282,7 @@ def _initialize_extensions(self, extension_point_id):
         return extensions
 
     def _translate_index(self, index, offset):
-        """ Translate an event index by the given offset. """
+        """Translate an event index by the given offset."""
 
         if isinstance(index, slice):
             index = slice(
diff --git a/envisage/resource/api.py b/envisage/resource/api.py
index f36d08921..d368b8292 100644
--- a/envisage/resource/api.py
+++ b/envisage/resource/api.py
@@ -7,11 +7,10 @@
 # is also available online at http://www.enthought.com/licenses/BSD.txt
 #
 # Thanks for using Enthought open source!
-from .i_resource_protocol import IResourceProtocol
-from .i_resource_manager import IResourceManager
-
 from .file_resource_protocol import FileResourceProtocol
 from .http_resource_protocol import HTTPResourceProtocol
+from .i_resource_manager import IResourceManager
+from .i_resource_protocol import IResourceProtocol
 from .no_such_resource_error import NoSuchResourceError
 from .package_resource_protocol import PackageResourceProtocol
 from .resource_manager import ResourceManager
diff --git a/envisage/resource/file_resource_protocol.py b/envisage/resource/file_resource_protocol.py
index 292c02429..a51332993 100644
--- a/envisage/resource/file_resource_protocol.py
+++ b/envisage/resource/file_resource_protocol.py
@@ -23,14 +23,14 @@
 
 @provides(IResourceProtocol)
 class FileResourceProtocol(HasTraits):
-    """ A resource protocol for a local file system. """
+    """A resource protocol for a local file system."""
 
     ###########################################################################
     # 'IResourceProtocol' interface.
     ###########################################################################
 
     def file(self, address):
-        """ Return a readable file-like object for the specified address. """
+        """Return a readable file-like object for the specified address."""
 
         # Opened in binary mode to be consistent with package resources. This
         # means, for example, that line-endings will not be converted.
diff --git a/envisage/resource/http_resource_protocol.py b/envisage/resource/http_resource_protocol.py
index d7a8f9981..26e32538e 100644
--- a/envisage/resource/http_resource_protocol.py
+++ b/envisage/resource/http_resource_protocol.py
@@ -19,14 +19,14 @@
 
 @provides(IResourceProtocol)
 class HTTPResourceProtocol(HasTraits):
-    """ A resource protocol for HTTP documents. """
+    """A resource protocol for HTTP documents."""
 
     ###########################################################################
     # 'IResourceProtocol' interface.
     ###########################################################################
 
     def file(self, address):
-        """ Return a readable file-like object for the specified address. """
+        """Return a readable file-like object for the specified address."""
 
         # Do the imports here 'cos I'm not sure how much this will actually
         # be used.
diff --git a/envisage/resource/i_resource_manager.py b/envisage/resource/i_resource_manager.py
index 5aad0c3c2..a5dcb70c0 100644
--- a/envisage/resource/i_resource_manager.py
+++ b/envisage/resource/i_resource_manager.py
@@ -18,13 +18,13 @@
 
 
 class IResourceManager(Interface):
-    """ The resource manager interface. """
+    """The resource manager interface."""
 
     # The protocols used by the manager to resolve resource URLs.
     resource_protocols = Instance(IResourceProtocol)
 
     def file(self, url):
-        """ Return a readable file-like object for the specified url.
+        """Return a readable file-like object for the specified url.
 
         Raise a 'NoSuchResourceError' if the resource does not exist.
 
diff --git a/envisage/resource/i_resource_protocol.py b/envisage/resource/i_resource_protocol.py
index 8ae0bda9a..5305a656a 100644
--- a/envisage/resource/i_resource_protocol.py
+++ b/envisage/resource/i_resource_protocol.py
@@ -15,10 +15,10 @@
 
 
 class IResourceProtocol(Interface):
-    """ The interface for protocols that handle resource URLs. """
+    """The interface for protocols that handle resource URLs."""
 
     def file(self, address):
-        """ Return a readable file-like object for the specified address.
+        """Return a readable file-like object for the specified address.
 
         Raise a 'NoSuchResourceError' if the resource does not exist.
 
diff --git a/envisage/resource/no_such_resource_error.py b/envisage/resource/no_such_resource_error.py
index e4408ca9b..1864f63d8 100644
--- a/envisage/resource/no_such_resource_error.py
+++ b/envisage/resource/no_such_resource_error.py
@@ -11,9 +11,9 @@
 
 
 class NoSuchResourceError(Exception):
-    """ The exception raised when trying to open a non-existent resource. """
+    """The exception raised when trying to open a non-existent resource."""
 
     def __init__(self, message=""):
-        """ Constructor. """
+        """Constructor."""
 
         Exception.__init__(self, message)
diff --git a/envisage/resource/package_resource_protocol.py b/envisage/resource/package_resource_protocol.py
index f7cb71c37..5ac040ceb 100644
--- a/envisage/resource/package_resource_protocol.py
+++ b/envisage/resource/package_resource_protocol.py
@@ -26,7 +26,7 @@
 
 @provides(IResourceProtocol)
 class PackageResourceProtocol(HasTraits):
-    """ A resource protocol for package resources.
+    """A resource protocol for package resources.
 
     This protocol uses 'importlib.resources' to find and access resources.
 
@@ -44,7 +44,7 @@ class PackageResourceProtocol(HasTraits):
     ###########################################################################
 
     def file(self, address):
-        """ Return a readable file-like object for the specified address. """
+        """Return a readable file-like object for the specified address."""
 
         package, *resource_path = address.split("/")
 
@@ -52,7 +52,7 @@ def file(self, address):
             raise NoSuchResourceError(address)
 
         try:
-            f = files(package).joinpath(*resource_path).open('rb')
+            f = files(package).joinpath(*resource_path).open("rb")
         except (
             ModuleNotFoundError,
             TypeError,  # TypeError is raised if package is a module
diff --git a/envisage/resource/resource_manager.py b/envisage/resource/resource_manager.py
index e91dfa93a..c6c6742b9 100644
--- a/envisage/resource/resource_manager.py
+++ b/envisage/resource/resource_manager.py
@@ -11,7 +11,7 @@
 
 
 # Enthought library imports.
-from traits.api import Dict, HasTraits, Str, provides
+from traits.api import Dict, HasTraits, provides, Str
 
 # Local imports.
 from .i_resource_manager import IResourceManager
@@ -20,7 +20,7 @@
 
 @provides(IResourceManager)
 class ResourceManager(HasTraits):
-    """ The default resource manager. """
+    """The default resource manager."""
 
     #### 'IResourceManager' interface #########################################
 
@@ -34,7 +34,7 @@ class ResourceManager(HasTraits):
     #### Trait initializers ###################################################
 
     def _resource_protocols_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # We do the import(s) here in case somebody wants a resource manager
         # that doesn't use the default protocol(s).
@@ -53,7 +53,7 @@ def _resource_protocols_default(self):
     #### Methods ##############################################################
 
     def file(self, url):
-        """ Return a readable file-like object for the specified url. """
+        """Return a readable file-like object for the specified url."""
 
         protocol_name, address = url.split("://")
 
diff --git a/envisage/resource/tests/test_resource_manager.py b/envisage/resource/tests/test_resource_manager.py
index 44c04e697..2f0fb1892 100644
--- a/envisage/resource/tests/test_resource_manager.py
+++ b/envisage/resource/tests/test_resource_manager.py
@@ -12,18 +12,18 @@
 
 # Standard library imports.
 import unittest
+import urllib.request
 from io import StringIO
 from urllib.error import HTTPError
-import urllib.request
+
 try:
-    from importlib.resources import files, as_file
+    from importlib.resources import as_file, files
 except ImportError:
-    from importlib_resources import files, as_file
+    from importlib_resources import as_file, files
 
 
 # Enthought library imports.
-from envisage.resource.api import ResourceManager
-from envisage.resource.api import NoSuchResourceError
+from envisage.resource.api import NoSuchResourceError, ResourceManager
 
 # Module to patch urlopen in during testing.
 url_library = urllib.request
@@ -48,20 +48,20 @@ def stubout_urlopen(url):
 
 
 class ResourceManagerTestCase(unittest.TestCase):
-    """ Tests for the resource manager. """
+    """Tests for the resource manager."""
 
     ###########################################################################
     # 'TestCase' interface.
     ###########################################################################
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         self.stored_urlopen = url_library.urlopen
         url_library.urlopen = stubout_urlopen
 
     def tearDown(self):
-        """ Called immediately after each test method has been called. """
+        """Called immediately after each test method has been called."""
 
         url_library.urlopen = self.stored_urlopen
 
@@ -70,14 +70,13 @@ def tearDown(self):
     ###########################################################################
 
     def test_file_resource(self):
-        """ file resource """
+        """file resource"""
 
         rm = ResourceManager()
 
         # Get the filename of the 'api.py' file.
         resource = files("envisage.resource") / "api.py"
         with as_file(resource) as path:
-
             # Open a file resource.
             f = rm.file(f"file://{path}")
             self.assertNotEqual(f, None)
@@ -89,7 +88,7 @@ def test_file_resource(self):
                 self.assertEqual(g.read(), contents)
 
     def test_no_such_file_resource(self):
-        """ no such file resource """
+        """no such file resource"""
 
         rm = ResourceManager()
 
@@ -98,7 +97,7 @@ def test_no_such_file_resource(self):
             rm.file("file://../bogus.py")
 
     def test_package_resource(self):
-        """ package resource """
+        """package resource"""
 
         rm = ResourceManager()
 
@@ -114,7 +113,7 @@ def test_package_resource(self):
             self.assertEqual(g.read(), contents)
 
     def test_package_resource_subdir(self):
-        """ package resource """
+        """package resource"""
 
         rm = ResourceManager()
 
@@ -130,7 +129,7 @@ def test_package_resource_subdir(self):
             self.assertEqual(g.read(), contents)
 
     def test_no_such_package_resource(self):
-        """ no such package resource """
+        """no such package resource"""
 
         rm = ResourceManager()
 
@@ -151,7 +150,7 @@ def test_no_such_package_resource(self):
             rm.file("pkgfile://envisage.resource.resource_manager/anything")
 
     def test_http_resource(self):
-        """ http resource """
+        """http resource"""
 
         # Open an HTTP document resource.
         rm = ResourceManager()
@@ -164,7 +163,7 @@ def test_http_resource(self):
         self.assertEqual(contents, "This is a test file.\n")
 
     def test_no_such_http_resource(self):
-        """ no such http resource """
+        """no such http resource"""
 
         # Open an HTTP document resource.
         rm = ResourceManager()
@@ -173,7 +172,7 @@ def test_no_such_http_resource(self):
             rm.file("http://localhost:1234/bogus.dat")
 
     def test_unknown_protocol(self):
-        """ unknown protocol """
+        """unknown protocol"""
 
         # Open an HTTP document resource.
         rm = ResourceManager()
diff --git a/envisage/service.py b/envisage/service.py
index 9c2b640d6..22e1cbb71 100644
--- a/envisage/service.py
+++ b/envisage/service.py
@@ -21,7 +21,7 @@
 
 
 class Service(TraitType):
-    """ A trait type used to access services.
+    """A trait type used to access services.
 
     Note that this is a trait *type* and hence does *NOT* have traits itself
     (i.e. it does *not* inherit from 'HasTraits').
@@ -35,7 +35,7 @@ class Service(TraitType):
     def __init__(
         self, protocol=None, query="", minimize="", maximize="", **metadata
     ):
-        """ Constructor. """
+        """Constructor."""
 
         super().__init__(**metadata)
 
@@ -52,7 +52,7 @@ def __init__(
         self._maximize = maximize
 
     def __repr__(self):
-        """ String representation of a Service object """
+        """String representation of a Service object"""
         return "Service(protocol={!r})".format(self._protocol)
 
     ###########################################################################
@@ -60,7 +60,7 @@ def __repr__(self):
     ###########################################################################
 
     def get(self, obj, trait_name):
-        """ Trait type getter. """
+        """Trait type getter."""
 
         service_registry = self._get_service_registry(obj)
 
@@ -71,7 +71,7 @@ def get(self, obj, trait_name):
         return obj
 
     def set(self, obj, name, value):
-        """ Trait type setter. """
+        """Trait type setter."""
 
         raise TraitError("Service traits cannot be set")
 
@@ -80,7 +80,7 @@ def set(self, obj, name, value):
     ###########################################################################
 
     def _get_service_registry(self, obj):
-        """ Return the service registry in effect for an object. """
+        """Return the service registry in effect for an object."""
 
         service_registry = getattr(obj, "service_registry", None)
         if service_registry is None:
diff --git a/envisage/service_offer.py b/envisage/service_offer.py
index b25cf8280..61ffa315d 100644
--- a/envisage/service_offer.py
+++ b/envisage/service_offer.py
@@ -15,7 +15,7 @@
 
 
 class ServiceOffer(HasTraits):
-    """ An offer to provide a service. """
+    """An offer to provide a service."""
 
     #### 'ServiceOffer' interface #############################################
 
diff --git a/envisage/service_registry.py b/envisage/service_registry.py
index 2bfab4d73..97d21e88c 100644
--- a/envisage/service_registry.py
+++ b/envisage/service_registry.py
@@ -20,18 +20,17 @@
 from .i_service_registry import IServiceRegistry
 from .import_manager import ImportManager
 
-
 # Logging.
 logger = logging.getLogger(__name__)
 
 
 class NoSuchServiceError(Exception):
-    """ Raised when a required service is not found. """
+    """Raised when a required service is not found."""
 
 
 @provides(IServiceRegistry)
 class ServiceRegistry(HasTraits):
-    """ The service registry. """
+    """The service registry."""
 
     ####  IServiceRegistry interface ##########################################
 
@@ -69,7 +68,7 @@ class ServiceRegistry(HasTraits):
     def get_required_service(
         self, protocol, query="", minimize="", maximize=""
     ):
-        """ Return the service that matches the specified query.
+        """Return the service that matches the specified query.
 
         Raise a 'NoSuchServiceError' exception if no such service exists.
 
@@ -82,7 +81,7 @@ def get_required_service(
         return service
 
     def get_service(self, protocol, query="", minimize="", maximize=""):
-        """ Return at most one service that matches the specified query. """
+        """Return at most one service that matches the specified query."""
 
         services = self.get_services(protocol, query, minimize, maximize)
         if len(services) > 0:
@@ -94,7 +93,7 @@ def get_service(self, protocol, query="", minimize="", maximize=""):
         return service
 
     def get_service_from_id(self, service_id):
-        """ Return the service with the specified id. """
+        """Return the service with the specified id."""
 
         try:
             protocol, obj, properties = self._services[service_id]
@@ -105,7 +104,7 @@ def get_service_from_id(self, service_id):
         return obj
 
     def get_services(self, protocol, query="", minimize="", maximize=""):
-        """ Return all services that match the specified query. """
+        """Return all services that match the specified query."""
 
         services = []
         for service_id, (name, obj, properties) in self._services.items():
@@ -140,7 +139,7 @@ def get_services(self, protocol, query="", minimize="", maximize=""):
         return services
 
     def get_service_properties(self, service_id):
-        """ Return the dictionary of properties associated with a service. """
+        """Return the dictionary of properties associated with a service."""
 
         try:
             protocol, obj, properties = self._services[service_id]
@@ -152,7 +151,7 @@ def get_service_properties(self, service_id):
         return properties
 
     def register_service(self, protocol, obj, properties=None):
-        """ Register a service. """
+        """Register a service."""
 
         protocol_name = self._get_protocol_name(protocol)
 
@@ -169,7 +168,7 @@ def register_service(self, protocol, obj, properties=None):
         return service_id
 
     def set_service_properties(self, service_id, properties):
-        """ Set the dictionary of properties associated with a service. """
+        """Set the dictionary of properties associated with a service."""
 
         try:
             protocol, obj, old_properties = self._services[service_id]
@@ -179,7 +178,7 @@ def set_service_properties(self, service_id, properties):
             raise ValueError("no service with id <%d>" % service_id)
 
     def unregister_service(self, service_id):
-        """ Unregister a service. """
+        """Unregister a service."""
 
         try:
             protocol, obj, properties = self._services.pop(service_id)
@@ -195,7 +194,7 @@ def unregister_service(self, service_id):
     ###########################################################################
 
     def _create_namespace(self, service, properties):
-        """ Create a namespace in which to evaluate a query. """
+        """Create a namespace in which to evaluate a query."""
 
         namespace = {}
         namespace.update(service.__dict__)
@@ -204,7 +203,7 @@ def _create_namespace(self, service, properties):
         return namespace
 
     def _eval_query(self, service, properties, query):
-        """ Evaluate a query over a single service.
+        """Evaluate a query over a single service.
 
         Return True if the service matches the query, otherwise return False.
 
@@ -220,7 +219,7 @@ def _eval_query(self, service, properties, query):
         return result
 
     def _get_protocol_name(self, protocol_or_name):
-        """ Returns the full class name for a protocol. """
+        """Returns the full class name for a protocol."""
 
         if isinstance(protocol_or_name, str):
             name = protocol_or_name
@@ -234,7 +233,7 @@ def _get_protocol_name(self, protocol_or_name):
         return name
 
     def _is_service_factory(self, protocol, obj):
-        """ Is the object a factory for services supporting the protocol? """
+        """Is the object a factory for services supporting the protocol?"""
 
         # fixme: Should we have a formal notion of service factory with an
         # appropriate API, or is this good enough? An API might have lifecycle
@@ -243,14 +242,14 @@ def _is_service_factory(self, protocol, obj):
         return not isinstance(obj, protocol)
 
     def _next_service_id(self):
-        """ Returns the next service ID. """
+        """Returns the next service ID."""
 
         self._service_id += 1
 
         return self._service_id
 
     def _resolve_factory(self, protocol, name, obj, properties, service_id):
-        """ If 'obj' is a factory then use it to create the actual service. """
+        """If 'obj' is a factory then use it to create the actual service."""
 
         # Is the registered service actually a service *factory*?
         if self._is_service_factory(protocol, obj):
diff --git a/envisage/tests/bad_eggs/acme-bad/acme_bad/bad_plugin.py b/envisage/tests/bad_eggs/acme-bad/acme_bad/bad_plugin.py
index cb0936a6e..6bbdc986f 100644
--- a/envisage/tests/bad_eggs/acme-bad/acme_bad/bad_plugin.py
+++ b/envisage/tests/bad_eggs/acme-bad/acme_bad/bad_plugin.py
@@ -10,16 +10,17 @@
 """ The 'Bar' plugin """
 
 
-# Enthought library imports.
-from envisage.api import Plugin
-from traits.api import Bool
-
 # Deliberate bad import
 import busted_module  # noqa: F401
 
+from traits.api import Bool
+
+# Enthought library imports.
+from envisage.api import Plugin
+
 
 class BadPlugin(Plugin):
-    """ The 'Bad' plugin """
+    """The 'Bad' plugin"""
 
     #### 'IPlugin' interface ##################################################
 
@@ -36,13 +37,13 @@ class BadPlugin(Plugin):
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
diff --git a/envisage/tests/bad_eggs/acme-bad/setup.py b/envisage/tests/bad_eggs/acme-bad/setup.py
index 8c55f7f7a..001a3a2fd 100644
--- a/envisage/tests/bad_eggs/acme-bad/setup.py
+++ b/envisage/tests/bad_eggs/acme-bad/setup.py
@@ -8,7 +8,7 @@
 #
 # Thanks for using Enthought open source!
 # Major package imports.
-from setuptools import setup, find_packages
+from setuptools import find_packages, setup
 
 setup(
     name="acme-bad",
diff --git a/envisage/tests/eggs/acme-bar/acme_bar/bar_plugin.py b/envisage/tests/eggs/acme-bar/acme_bar/bar_plugin.py
index b6f3e34aa..911b40dc5 100644
--- a/envisage/tests/eggs/acme-bar/acme_bar/bar_plugin.py
+++ b/envisage/tests/eggs/acme-bar/acme_bar/bar_plugin.py
@@ -10,13 +10,14 @@
 """ The 'Bar' plugin """
 
 
+from traits.api import Bool
+
 # Enthought library imports.
 from envisage.api import Plugin
-from traits.api import Bool
 
 
 class BarPlugin(Plugin):
-    """ The 'Bar' plugin """
+    """The 'Bar' plugin"""
 
     #### 'IPlugin' interface ##################################################
 
@@ -33,13 +34,13 @@ class BarPlugin(Plugin):
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
diff --git a/envisage/tests/eggs/acme-bar/setup.py b/envisage/tests/eggs/acme-bar/setup.py
index b23492d54..690e416f9 100644
--- a/envisage/tests/eggs/acme-bar/setup.py
+++ b/envisage/tests/eggs/acme-bar/setup.py
@@ -8,7 +8,7 @@
 #
 # Thanks for using Enthought open source!
 # Major package imports.
-from setuptools import setup, find_packages
+from setuptools import find_packages, setup
 
 setup(
     name="acme-bar",
diff --git a/envisage/tests/eggs/acme-baz/acme_baz/baz_plugin.py b/envisage/tests/eggs/acme-baz/acme_baz/baz_plugin.py
index fe9abfbce..5c3899615 100644
--- a/envisage/tests/eggs/acme-baz/acme_baz/baz_plugin.py
+++ b/envisage/tests/eggs/acme-baz/acme_baz/baz_plugin.py
@@ -10,13 +10,14 @@
 """ The 'Baz' plugin """
 
 
+from traits.api import Bool
+
 # Enthought library imports.
 from envisage.api import Plugin
-from traits.api import Bool
 
 
 class BazPlugin(Plugin):
-    """ The 'Baz' plugin """
+    """The 'Baz' plugin"""
 
     #### 'IPlugin' interface ##################################################
 
@@ -33,13 +34,13 @@ class BazPlugin(Plugin):
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
diff --git a/envisage/tests/eggs/acme-baz/setup.py b/envisage/tests/eggs/acme-baz/setup.py
index 3354345f0..19cc430d2 100644
--- a/envisage/tests/eggs/acme-baz/setup.py
+++ b/envisage/tests/eggs/acme-baz/setup.py
@@ -8,7 +8,7 @@
 #
 # Thanks for using Enthought open source!
 # Major package imports.
-from setuptools import setup, find_packages
+from setuptools import find_packages, setup
 
 setup(
     name="acme-baz",
diff --git a/envisage/tests/eggs/acme-foo/acme_foo/foo_plugin.py b/envisage/tests/eggs/acme-foo/acme_foo/foo_plugin.py
index b13eb8a92..5417af44e 100644
--- a/envisage/tests/eggs/acme-foo/acme_foo/foo_plugin.py
+++ b/envisage/tests/eggs/acme-foo/acme_foo/foo_plugin.py
@@ -10,13 +10,14 @@
 """ The 'Foo' plugin """
 
 
+from traits.api import Bool
+
 # Enthought library imports.
 from envisage.api import Plugin
-from traits.api import Bool
 
 
 class FooPlugin(Plugin):
-    """ The 'Foo' plugin """
+    """The 'Foo' plugin"""
 
     #### 'IPlugin' interface ##################################################
 
@@ -33,13 +34,13 @@ class FooPlugin(Plugin):
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
diff --git a/envisage/tests/eggs/acme-foo/setup.py b/envisage/tests/eggs/acme-foo/setup.py
index e36698360..36733a14a 100644
--- a/envisage/tests/eggs/acme-foo/setup.py
+++ b/envisage/tests/eggs/acme-foo/setup.py
@@ -8,7 +8,7 @@
 #
 # Thanks for using Enthought open source!
 # Major package imports.
-from setuptools import setup, find_packages
+from setuptools import find_packages, setup
 
 setup(
     name="acme-foo",
diff --git a/envisage/tests/event_tracker.py b/envisage/tests/event_tracker.py
index 3d5aadc84..1e59b24fa 100644
--- a/envisage/tests/event_tracker.py
+++ b/envisage/tests/event_tracker.py
@@ -16,7 +16,7 @@
 
 
 class EventTracker(HasTraits):
-    """ Used to track traits events. """
+    """Used to track traits events."""
 
     # The traits events that have fired.
     #
@@ -49,7 +49,7 @@ class EventTracker(HasTraits):
 
     @observe("subscriptions")
     def _update_listeners_on_all_subscriptions(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
         old, new = event.old, event.new
         for subscription in old:
             self._remove_subscription(subscription)
@@ -59,7 +59,7 @@ def _update_listeners_on_all_subscriptions(self, event):
 
     @observe("subscriptions:items")
     def _update_listeners_on_changed_subscriptions(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         for subscription in event.removed:
             self._remove_subscription(subscription)
@@ -68,7 +68,7 @@ def _update_listeners_on_changed_subscriptions(self, event):
             self._add_subscription(subscription)
 
     def _listener(self, obj, trait_name, old, new):
-        """ Dynamic trait change listener. """
+        """Dynamic trait change listener."""
 
         self.events.append((obj, trait_name, old, new))
         self.event_names.append(trait_name)
@@ -76,7 +76,7 @@ def _listener(self, obj, trait_name, old, new):
     #### Methods ##############################################################
 
     def _add_subscription(self, subscription):
-        """ Add a subscription. """
+        """Add a subscription."""
 
         obj, trait_name = subscription
 
@@ -87,7 +87,7 @@ def _add_subscription(self, subscription):
             obj.on_trait_change(self._listener)
 
     def _remove_subscription(self, subscription):
-        """ Remove a subscription. """
+        """Remove a subscription."""
 
         obj, trait_name = subscription
 
diff --git a/envisage/tests/mutable_extension_registry.py b/envisage/tests/mutable_extension_registry.py
index 1b7c18489..405adc43f 100644
--- a/envisage/tests/mutable_extension_registry.py
+++ b/envisage/tests/mutable_extension_registry.py
@@ -15,19 +15,19 @@
 
 
 class MutableExtensionRegistry(ExtensionRegistry):
-    """ A mutable, manually populated extension registry used for testing. """
+    """A mutable, manually populated extension registry used for testing."""
 
     ###########################################################################
     # 'MutableExtensionRegistry' interface.
     ###########################################################################
 
     def add_extension(self, extension_point_id, extension):
-        """ Contribute an extension to an extension point. """
+        """Contribute an extension to an extension point."""
 
         self.add_extensions(extension_point_id, [extension])
 
     def add_extensions(self, extension_point_id, extensions):
-        """ Contribute a list of extensions to an extension point. """
+        """Contribute a list of extensions to an extension point."""
 
         self._check_extension_point(extension_point_id)
 
@@ -40,12 +40,12 @@ def add_extensions(self, extension_point_id, extensions):
         self._call_listeners(refs, extension_point_id, extensions, [], index)
 
     def remove_extension(self, extension_point_id, extension):
-        """ Remove a contribution from an extension point. """
+        """Remove a contribution from an extension point."""
 
         self.remove_extensions(extension_point_id, [extension])
 
     def remove_extensions(self, extension_point_id, extensions):
-        """ Remove a list of contributions from an extension point. """
+        """Remove a list of contributions from an extension point."""
 
         for extension in extensions:
             try:
diff --git a/envisage/tests/plugins/banana/banana_plugin.py b/envisage/tests/plugins/banana/banana_plugin.py
index 5e9369b26..3a5c35b1f 100644
--- a/envisage/tests/plugins/banana/banana_plugin.py
+++ b/envisage/tests/plugins/banana/banana_plugin.py
@@ -10,12 +10,13 @@
 """ The 'Banana' plugin """
 
 
-from envisage.api import Plugin
 from traits.api import Bool
 
+from envisage.api import Plugin
+
 
 class BananaPlugin(Plugin):
-    """ The 'Banana' plugin """
+    """The 'Banana' plugin"""
 
     #### 'IPlugin' protocol ###################################################
 
@@ -23,13 +24,13 @@ class BananaPlugin(Plugin):
     id = "banana"
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
diff --git a/envisage/tests/plugins/banana/plugins.py b/envisage/tests/plugins/banana/plugins.py
index a9e1f4869..37204f9f3 100644
--- a/envisage/tests/plugins/banana/plugins.py
+++ b/envisage/tests/plugins/banana/plugins.py
@@ -11,7 +11,7 @@
 
 
 def get_plugins():
-    """ Get the plugins from this package. """
+    """Get the plugins from this package."""
 
     from .banana_plugin import BananaPlugin
 
diff --git a/envisage/tests/plugins/orange/orange_plugin.py b/envisage/tests/plugins/orange/orange_plugin.py
index ddf5da8d3..a121b16db 100644
--- a/envisage/tests/plugins/orange/orange_plugin.py
+++ b/envisage/tests/plugins/orange/orange_plugin.py
@@ -10,12 +10,13 @@
 """ The 'Orange' plugin """
 
 
-from envisage.api import Plugin
 from traits.api import Bool
 
+from envisage.api import Plugin
+
 
 class OrangePlugin(Plugin):
-    """ The 'Orange' plugin """
+    """The 'Orange' plugin"""
 
     #### 'IPlugin' protocol ###################################################
 
@@ -23,13 +24,13 @@ class OrangePlugin(Plugin):
     id = "orange"
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
diff --git a/envisage/tests/plugins/orange/plugins.py b/envisage/tests/plugins/orange/plugins.py
index 080096d94..46cfd1825 100644
--- a/envisage/tests/plugins/orange/plugins.py
+++ b/envisage/tests/plugins/orange/plugins.py
@@ -11,7 +11,7 @@
 
 
 def get_plugins():
-    """ Get the plugins from this package. """
+    """Get the plugins from this package."""
 
     from .orange_plugin import OrangePlugin
 
diff --git a/envisage/tests/plugins/pear/pear_plugin.py b/envisage/tests/plugins/pear/pear_plugin.py
index d973a05f2..c22e54c25 100644
--- a/envisage/tests/plugins/pear/pear_plugin.py
+++ b/envisage/tests/plugins/pear/pear_plugin.py
@@ -10,12 +10,13 @@
 """ The 'Pear' plugin """
 
 
-from envisage.api import Plugin
 from traits.api import Bool
 
+from envisage.api import Plugin
+
 
 class PearPlugin(Plugin):
-    """ The 'Pear' plugin """
+    """The 'Pear' plugin"""
 
     #### 'IPlugin' protocol ###################################################
 
@@ -23,13 +24,13 @@ class PearPlugin(Plugin):
     id = "pear"
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
diff --git a/envisage/tests/support.py b/envisage/tests/support.py
index 5c6223ccb..348aed47c 100644
--- a/envisage/tests/support.py
+++ b/envisage/tests/support.py
@@ -23,7 +23,6 @@
 
 from envisage.api import Application, ExtensionPoint, Plugin
 
-
 # Skip decorator for tests that require a working GUI instance.
 try:
     GUI()
@@ -51,30 +50,32 @@
 
 # Application class used in various tests.
 
+
 class SimpleApplication(Application):
-    """ The type of application used in the tests. """
+    """The type of application used in the tests."""
 
     id = "test"
 
 
 # Plugins used in multiple tests.
 
+
 class PluginA(Plugin):
-    """ A plugin that offers an extension point. """
+    """A plugin that offers an extension point."""
 
     id = "A"
     x = ExtensionPoint(List, id="a.x")
 
 
 class PluginB(Plugin):
-    """ A plugin that contributes to an extension point. """
+    """A plugin that contributes to an extension point."""
 
     id = "B"
     x = List(Int, [1, 2, 3], contributes_to="a.x")
 
 
 class PluginC(Plugin):
-    """ Another plugin that contributes to an extension point! """
+    """Another plugin that contributes to an extension point!"""
 
     id = "C"
     x = List(Int, [98, 99, 100], contributes_to="a.x")
diff --git a/envisage/tests/test_api.py b/envisage/tests/test_api.py
index e11be4658..48c5e7d98 100644
--- a/envisage/tests/test_api.py
+++ b/envisage/tests/test_api.py
@@ -15,13 +15,15 @@
 
 
 class TestApi(unittest.TestCase):
-    """ Test for API """
+    """Test for API"""
+
     def test_import(self):
         self.assertEqual(api.BINDINGS, ids.BINDINGS)
         self.assertEqual(api.COMMANDS, ids.COMMANDS)
         self.assertEqual(api.PREFERENCES, ids.PREFERENCES)
-        self.assertEqual(api.PREFERENCES_CATEGORIES,
-                         ids.PREFERENCES_CATEGORIES)
+        self.assertEqual(
+            api.PREFERENCES_CATEGORIES, ids.PREFERENCES_CATEGORIES
+        )
         self.assertEqual(api.PREFERENCES_PANES, ids.PREFERENCES_PANES)
         self.assertEqual(api.SERVICE_OFFERS, ids.SERVICE_OFFERS)
         self.assertEqual(api.TASKS, ids.TASKS)
diff --git a/envisage/tests/test_application.py b/envisage/tests/test_application.py
index f6a3509f4..2dea7de4c 100644
--- a/envisage/tests/test_application.py
+++ b/envisage/tests/test_application.py
@@ -15,31 +15,27 @@
 import shutil
 import unittest
 
+from traits.api import Bool, Int, List
+
 # Enthought library imports.
 from traits.etsconfig.api import ETSConfig
-from envisage.api import ExtensionPoint
-from envisage.api import Plugin, PluginManager
-from traits.api import Bool, Int, List
+
+from envisage.api import ExtensionPoint, Plugin, PluginManager
+from envisage.tests.ets_config_patcher import ETSConfigPatcher
 
 # Local imports.
 from envisage.tests.event_tracker import EventTracker
-from envisage.tests.ets_config_patcher import ETSConfigPatcher
-from envisage.tests.support import (
-    PluginA,
-    PluginB,
-    PluginC,
-    SimpleApplication,
-)
+from envisage.tests.support import PluginA, PluginB, PluginC, SimpleApplication
 
 
 def vetoer(event):
-    """ An observer that will veto an event. """
+    """An observer that will veto an event."""
 
     event.new.veto = True
 
 
 class SimplePlugin(Plugin):
-    """ A simple plugin. """
+    """A simple plugin."""
 
     #### 'SimplePlugin' interface #############################################
 
@@ -51,32 +47,32 @@ class SimplePlugin(Plugin):
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
 
 
 class BadPlugin(Plugin):
-    """ A plugin that just causes trouble ;^). """
+    """A plugin that just causes trouble ;^)."""
 
     ###########################################################################
     # 'IPlugin' interface.
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         raise 1 / 0
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         raise 1 / 0
 
@@ -87,8 +83,8 @@ def stop(self):
 
 
 class PluginD(Plugin):
-    """ Plugin that expects to be started before contributing to
-    extension points. """
+    """Plugin that expects to be started before contributing to
+    extension points."""
 
     id = "D"
     x = ExtensionPoint(List, id="d.x")
@@ -108,8 +104,8 @@ def _y_default(self):
 
 
 class PluginE(Plugin):
-    """ Another plugin that expects to be started before contributing to
-    extension points. """
+    """Another plugin that expects to be started before contributing to
+    extension points."""
 
     id = "E"
     x = ExtensionPoint(List, id="e.x")
@@ -129,17 +125,17 @@ def _y_default(self):
 
 
 class ApplicationTestCase(unittest.TestCase):
-    """ Tests for applications and plugins. """
+    """Tests for applications and plugins."""
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         ets_config_patcher = ETSConfigPatcher()
         ets_config_patcher.start()
         self.addCleanup(ets_config_patcher.stop)
 
     def test_home(self):
-        """ home """
+        """home"""
 
         application = SimpleApplication()
 
@@ -159,7 +155,7 @@ def test_home(self):
         shutil.rmtree(application.home)
 
     def test_no_plugins(self):
-        """ no plugins """
+        """no plugins"""
 
         application = SimpleApplication()
 
@@ -185,7 +181,7 @@ def test_no_plugins(self):
         )
 
     def test_veto_starting(self):
-        """ veto starting """
+        """veto starting"""
 
         application = SimpleApplication()
 
@@ -207,7 +203,7 @@ def test_veto_starting(self):
         self.assertTrue("started" not in tracker.event_names)
 
     def test_veto_stopping(self):
-        """ veto stopping """
+        """veto stopping"""
 
         application = SimpleApplication()
 
@@ -234,7 +230,7 @@ def test_veto_stopping(self):
         self.assertTrue("stopped" not in tracker.event_names)
 
     def test_start_and_stop_errors(self):
-        """ start and stop errors """
+        """start and stop errors"""
 
         simple_plugin = SimplePlugin()
         bad_plugin = BadPlugin()
@@ -257,7 +253,7 @@ def test_start_and_stop_errors(self):
             application.stop_plugin(plugin_id="bogus")
 
     def test_extension_point(self):
-        """ extension point """
+        """extension point"""
 
         a = PluginA()
         b = PluginB()
@@ -298,7 +294,7 @@ def test_extension_point_resolution_occurs_after_plugin_start(self):
         )
 
     def test_add_extension_point_listener(self):
-        """ add extension point listener """
+        """add extension point listener"""
 
         a = PluginA()
         b = PluginB()
@@ -309,7 +305,7 @@ def test_add_extension_point_listener(self):
         application.start()
 
         def listener(extension_registry, event):
-            """ An extension point listener. """
+            """An extension point listener."""
 
             listener.extension_point_id = event.extension_point_id
             listener.added = event.added
@@ -332,7 +328,7 @@ def listener(extension_registry, event):
         self.assertEqual([98, 99, 100], listener.added)
 
     def test_remove_extension_point_listener(self):
-        """ remove extension point listener """
+        """remove extension point listener"""
 
         a = PluginA()
         b = PluginB()
@@ -343,7 +339,7 @@ def test_remove_extension_point_listener(self):
         application.start()
 
         def listener(extension_registry, event):
-            """ An extension point listener. """
+            """An extension point listener."""
 
             listener.extension_point_id = event.extension_point_id
             listener.added = event.added
@@ -375,7 +371,7 @@ def listener(extension_registry, event):
         self.assertEqual(None, listener.extension_point_id)
 
     def test_add_plugin(self):
-        """ add plugin """
+        """add plugin"""
 
         a = PluginA()
         b = PluginB()
@@ -409,7 +405,7 @@ def test_add_plugin(self):
         self.assertEqual([1, 2, 3, 98, 99, 100], extensions)
 
     def test_get_plugin(self):
-        """ get plugin """
+        """get plugin"""
 
         a = PluginA()
         b = PluginB()
@@ -428,7 +424,7 @@ def test_get_plugin(self):
         self.assertEqual(None, application.get_plugin("BOGUS"))
 
     def test_remove_plugin(self):
-        """ remove plugin """
+        """remove plugin"""
 
         a = PluginA()
         b = PluginB()
@@ -461,7 +457,7 @@ def test_remove_plugin(self):
         self.assertEqual([98, 99, 100], extensions)
 
     def test_set_plugin_manager_at_contruction_time(self):
-        """ set plugin manager at construction time"""
+        """set plugin manager at construction time"""
 
         a = PluginA()
         b = PluginB()
diff --git a/envisage/tests/test_composite_plugin_manager.py b/envisage/tests/test_composite_plugin_manager.py
index b66669228..7e103bc48 100644
--- a/envisage/tests/test_composite_plugin_manager.py
+++ b/envisage/tests/test_composite_plugin_manager.py
@@ -11,15 +11,16 @@
 
 import unittest
 
+from traits.api import Bool
+
 from envisage.application import Application
 from envisage.composite_plugin_manager import CompositePluginManager
-from envisage.plugin_manager import PluginManager
 from envisage.plugin import Plugin
-from traits.api import Bool
+from envisage.plugin_manager import PluginManager
 
 
 class SimplePlugin(Plugin):
-    """ A simple plugin. """
+    """A simple plugin."""
 
     #### 'SimplePlugin' protocol ##############################################
 
@@ -29,43 +30,41 @@ class SimplePlugin(Plugin):
     #### 'IPlugin' protocol ###################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
 
 
 class CustomException(Exception):
-    """ Custom exception used for testing purposes. """
+    """Custom exception used for testing purposes."""
 
     pass
 
 
 class RaisingPluginManager(PluginManager):
-    """ A PluginManager that raises on iteration. """
+    """A PluginManager that raises on iteration."""
 
     def __iter__(self):
         raise CustomException("Something went wrong.")
 
 
 class CompositePluginManagerTestCase(unittest.TestCase):
-    """ Tests for the composite plugin manager. """
+    """Tests for the composite plugin manager."""
 
     def test_find_no_plugins_if_there_are_no_plugin_managers(self):
-
         plugin_manager = CompositePluginManager()
         ids = [plugin.id for plugin in plugin_manager]
 
         self.assertEqual(0, len(ids))
 
     def test_find_no_plugins_if_there_are_no_plugins_in_plugin_managers(self):
-
         plugin_manager = CompositePluginManager(
             plugin_managers=[PluginManager(), PluginManager()]
         )
@@ -74,7 +73,6 @@ def test_find_no_plugins_if_there_are_no_plugins_in_plugin_managers(self):
         self.assertEqual(0, len(ids))
 
     def test_find_plugins_in_a_single_plugin_manager(self):
-
         plugin_manager = CompositePluginManager(
             plugin_managers=[
                 PluginManager(
@@ -91,7 +89,6 @@ def test_find_plugins_in_a_single_plugin_manager(self):
         self._test_start_and_stop(plugin_manager, ["red", "yellow"])
 
     def test_find_plugins_in_a_multiple_plugin_managers(self):
-
         plugin_manager = CompositePluginManager(
             plugin_managers=[
                 PluginManager(
@@ -110,7 +107,6 @@ def test_find_plugins_in_a_multiple_plugin_managers(self):
         self._test_start_and_stop(plugin_manager, ["red", "yellow", "green"])
 
     def test_application_gets_propogated_to_plugin_managers(self):
-
         application = Application()
 
         composite_plugin_manager = CompositePluginManager(
@@ -124,7 +120,6 @@ def test_application_gets_propogated_to_plugin_managers(self):
     def test_propogate_plugin_added_or_remove_events_from_plugin_managers(
         self,
     ):
-
         a = PluginManager()
         b = PluginManager()
 
@@ -164,7 +159,7 @@ def test_correct_exception_propagated_from_plugin_manager(self):
     #### Private protocol #####################################################
 
     def _plugin_count(self, plugin_manager):
-        """ Return how many plugins the plugin manager contains. """
+        """Return how many plugins the plugin manager contains."""
 
         count = 0
         for plugin in plugin_manager:
@@ -173,8 +168,8 @@ def _plugin_count(self, plugin_manager):
         return count
 
     def _test_start_and_stop(self, plugin_manager, expected):
-        """ Make sure the plugin manager starts and stops the expected plugins.
-
+        """
+        Make sure the plugin manager starts and stops the expected plugins.
         """
 
         # Make sure the plugin manager found only the required plugins.
diff --git a/envisage/tests/test_core_plugin.py b/envisage/tests/test_core_plugin.py
index a3f93393e..6115435bd 100644
--- a/envisage/tests/test_core_plugin.py
+++ b/envisage/tests/test_core_plugin.py
@@ -15,21 +15,21 @@
 # Major package imports.
 from pkg_resources import resource_filename
 
+from traits.api import HasTraits, Interface, List, on_trait_change, Str
+
 # Enthought library imports.
-from envisage.api import CorePlugin, Plugin
-from envisage.api import ServiceOffer
+from envisage.api import CorePlugin, Plugin, ServiceOffer
 from envisage.tests.support import SimpleApplication
-from traits.api import HasTraits, Interface, List, on_trait_change, Str
 
 # This module's package.
 PKG = "envisage.tests"
 
 
 class CorePluginTestCase(unittest.TestCase):
-    """ Tests for the core plugin. """
+    """Tests for the core plugin."""
 
     def test_service_offers(self):
-        """ service offers """
+        """service offers"""
 
         class IMyService(Interface):
             pass
@@ -40,7 +40,7 @@ class PluginA(Plugin):
             service_offers = List(contributes_to="envisage.service_offers")
 
             def _service_offers_default(self):
-                """ Trait initializer. """
+                """Trait initializer."""
 
                 service_offers = [
                     ServiceOffer(
@@ -51,7 +51,7 @@ def _service_offers_default(self):
                 return service_offers
 
             def _my_service_factory(self, **properties):
-                """ Service factory. """
+                """Service factory."""
 
                 return 42
 
@@ -71,7 +71,7 @@ def _my_service_factory(self, **properties):
         self.assertEqual(None, application.get_service(IMyService))
 
     def test_dynamically_added_service_offer(self):
-        """ dynamically added service offer """
+        """dynamically added service offer"""
 
         class IMyService(Interface):
             pass
@@ -82,7 +82,7 @@ class PluginA(Plugin):
             service_offers = List(contributes_to="envisage.service_offers")
 
             def _service_offers_default(self):
-                """ Trait initializer. """
+                """Trait initializer."""
 
                 service_offers = [
                     ServiceOffer(
@@ -93,7 +93,7 @@ def _service_offers_default(self):
                 return service_offers
 
             def _my_service_factory(self, **properties):
-                """ Service factory. """
+                """Service factory."""
 
                 return 42
 
@@ -125,14 +125,14 @@ def _my_service_factory(self, **properties):
         self.assertEqual(42, service)
 
     def test_preferences(self):
-        """ preferences """
+        """preferences"""
 
         class PluginA(Plugin):
             id = "A"
             preferences = List(contributes_to="envisage.preferences")
 
             def _preferences_default(self):
-                """ Trait initializer. """
+                """Trait initializer."""
 
                 return ["file://" + resource_filename(PKG, "preferences.ini")]
 
@@ -146,14 +146,14 @@ def _preferences_default(self):
         self.assertEqual("42", application.preferences.get("enthought.test.x"))
 
     def test_dynamically_added_preferences(self):
-        """ dynamically added preferences """
+        """dynamically added preferences"""
 
         class PluginA(Plugin):
             id = "A"
             preferences = List(contributes_to="envisage.preferences")
 
             def _preferences_default(self):
-                """ Trait initializer. """
+                """Trait initializer."""
 
                 return ["file://" + resource_filename(PKG, "preferences.ini")]
 
@@ -172,7 +172,7 @@ def _preferences_default(self):
 
     # regression test for enthought/envisage#251
     def test_unregister_service_offer(self):
-        """ Unregister a service that is contributed to the
+        """Unregister a service that is contributed to the
         "envisage.service_offers" extension point while the application is
         running.
         """
@@ -190,7 +190,6 @@ class PluginA(Plugin):
             service_offers = List(contributes_to=SERVICE_OFFERS)
 
             def _service_offers_default(self):
-
                 a_service_offer = ServiceOffer(
                     protocol=IJunk,
                     factory=self._create_junk_service,
@@ -199,7 +198,7 @@ def _service_offers_default(self):
                 return [a_service_offer]
 
             def _create_junk_service(self):
-                """ Factory method for the 'Junk' service. """
+                """Factory method for the 'Junk' service."""
 
                 return Junk()
 
@@ -216,9 +215,9 @@ def _unregister_junk_service(self):
         application.run()
 
     def test_unregister_service(self):
-        """ Unregister a service which was registered on the application
+        """Unregister a service which was registered on the application
         directly, not through the CorePlugin's extension point. CorePlugin
-        should not do anything to interfere. """
+        should not do anything to interfere."""
 
         class IJunk(Interface):
             trash = Str()
diff --git a/envisage/tests/test_egg_based.py b/envisage/tests/test_egg_based.py
index e9de3c354..b953ef1a7 100644
--- a/envisage/tests/test_egg_based.py
+++ b/envisage/tests/test_egg_based.py
@@ -10,12 +10,12 @@
 """ Base class for Egg-based test cases. """
 
 
-from os.path import join
 import shutil
 import subprocess
 import sys
 import tempfile
 import unittest
+from os.path import join
 
 import pkg_resources
 
@@ -49,7 +49,7 @@ def build_egg(egg_dir, dist_dir):
 
 
 class EggBasedTestCase(unittest.TestCase):
-    """ Base class for Egg-based test cases. """
+    """Base class for Egg-based test cases."""
 
     @classmethod
     def setUpClass(cls):
@@ -58,7 +58,8 @@ def setUpClass(cls):
         """
         cls.egg_dir = tempfile.mkdtemp()
         eggs_root_dir = pkg_resources.resource_filename(
-            "envisage.tests", "eggs")
+            "envisage.tests", "eggs"
+        )
         for egg_name in ["acme-bar", "acme-baz", "acme-foo"]:
             build_egg(
                 egg_dir=join(eggs_root_dir, egg_name),
@@ -73,14 +74,14 @@ def tearDownClass(cls):
         shutil.rmtree(cls.egg_dir)
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         # Some tests cause sys.path to be modified. Capture the original
         # contents so that we can restore sys.path later.
         self._original_sys_path_contents = sys.path[:]
 
     def tearDown(self):
-        """ Called immediately after each test method has been called. """
+        """Called immediately after each test method has been called."""
 
         # Undo any sys.path modifications
         sys.path[:] = self._original_sys_path_contents
@@ -88,7 +89,7 @@ def tearDown(self):
         pkg_resources.working_set = pkg_resources.WorkingSet()
 
     def _add_egg(self, filename, working_set=None):
-        """ Create and add a distribution from the specified '.egg'. """
+        """Create and add a distribution from the specified '.egg'."""
 
         if working_set is None:
             working_set = pkg_resources.working_set
@@ -105,7 +106,7 @@ def _add_egg(self, filename, working_set=None):
             working_set.add(distribution)
 
     def _add_eggs_on_path(self, path, working_set=None):
-        """ Add all eggs found on the path to a working set. """
+        """Add all eggs found on the path to a working set."""
 
         if working_set is None:
             working_set = pkg_resources.working_set
diff --git a/envisage/tests/test_egg_basket_plugin_manager.py b/envisage/tests/test_egg_basket_plugin_manager.py
index 2bddfae4c..1dfabaf1c 100644
--- a/envisage/tests/test_egg_basket_plugin_manager.py
+++ b/envisage/tests/test_egg_basket_plugin_manager.py
@@ -10,11 +10,11 @@
 """ Tests for the 'Egg Basket' plugin manager. """
 
 import glob
-from os.path import basename, join
 import shutil
 import sys
 import tempfile
 import unittest
+from os.path import basename, join
 
 import pkg_resources
 
@@ -23,7 +23,7 @@
 
 
 class EggBasketPluginManagerTestCase(unittest.TestCase):
-    """ Tests for the 'Egg Basket' plugin manager. """
+    """Tests for the 'Egg Basket' plugin manager."""
 
     #### 'unittest.TestCase' protocol #########################################
 
@@ -36,7 +36,8 @@ def setUpClass(cls):
         cls.bad_eggs_dir = tempfile.mkdtemp()
 
         eggs_root_dir = pkg_resources.resource_filename(
-            "envisage.tests", "eggs")
+            "envisage.tests", "eggs"
+        )
         for egg_name in ["acme-bar", "acme-baz", "acme-foo"]:
             build_egg(
                 egg_dir=join(eggs_root_dir, egg_name),
@@ -44,7 +45,8 @@ def setUpClass(cls):
             )
 
         bad_eggs_root_dir = pkg_resources.resource_filename(
-            "envisage.tests", "bad_eggs")
+            "envisage.tests", "bad_eggs"
+        )
         for egg_name in ["acme-bad"]:
             build_egg(
                 egg_dir=join(bad_eggs_root_dir, egg_name),
@@ -60,14 +62,14 @@ def tearDownClass(cls):
         shutil.rmtree(cls.eggs_dir)
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         # Some tests cause sys.path to be modified. Capture the original
         # contents so that we can restore sys.path later.
         self._original_sys_path_contents = sys.path[:]
 
     def tearDown(self):
-        """ Called immediately after each test method has been called. """
+        """Called immediately after each test method has been called."""
 
         # Undo any sys.path modifications
         sys.path[:] = self._original_sys_path_contents
@@ -79,7 +81,6 @@ def tearDown(self):
     #### Tests ################################################################
 
     def test_find_plugins_in_eggs_on_the_plugin_path(self):
-
         with self.assertWarns(DeprecationWarning):
             plugin_manager = EggBasketPluginManager(
                 plugin_path=[self.eggs_dir]
@@ -92,7 +93,6 @@ def test_find_plugins_in_eggs_on_the_plugin_path(self):
         self.assertIn("acme.baz", ids)
 
     def test_only_find_plugins_whose_ids_are_in_the_include_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         include = ["acme.foo", "acme.bar"]
@@ -110,7 +110,6 @@ def test_only_find_plugins_whose_ids_are_in_the_include_list(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_only_find_plugins_matching_a_wildcard_in_the_include_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         include = ["acme.b*"]
@@ -128,7 +127,6 @@ def test_only_find_plugins_matching_a_wildcard_in_the_include_list(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_ignore_plugins_whose_ids_are_in_the_exclude_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         exclude = ["acme.foo", "acme.baz"]
@@ -146,7 +144,6 @@ def test_ignore_plugins_whose_ids_are_in_the_exclude_list(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_ignore_plugins_matching_a_wildcard_in_the_exclude_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         exclude = ["acme.b*"]
@@ -265,8 +262,8 @@ def on_broken_distribution(dist, exc):
     #### Private protocol #####################################################
 
     def _test_start_and_stop(self, plugin_manager, expected):
-        """ Make sure the plugin manager starts and stops the expected plugins.
-
+        """
+        Make sure the plugin manager starts and stops the expected plugins.
         """
 
         # Make sure the plugin manager found only the required plugins.
@@ -293,7 +290,7 @@ def _test_start_and_stop(self, plugin_manager, expected):
             self.assertEqual(True, plugin.stopped)
 
     def _create_broken_distribution_eggdir(self, egg_pat, replacement=None):
-        """ Copy a good egg to a different version egg name in a new temp dir
+        """Copy a good egg to a different version egg name in a new temp dir
         and return the new directory.
 
         Parameters
diff --git a/envisage/tests/test_egg_plugin_manager.py b/envisage/tests/test_egg_plugin_manager.py
index cd2621bfe..91ab73bb6 100644
--- a/envisage/tests/test_egg_plugin_manager.py
+++ b/envisage/tests/test_egg_plugin_manager.py
@@ -20,7 +20,7 @@
 
 
 class EggPluginManagerTestCase(EggBasedTestCase):
-    """ Tests for the Egg plugin manager. """
+    """Tests for the Egg plugin manager."""
 
     ###########################################################################
     # Tests.
@@ -29,7 +29,7 @@ class EggPluginManagerTestCase(EggBasedTestCase):
     # fixme: Depending how many eggs are on sys.path, this test may take too
     # long to be part of the TDD cycle.
     def test_no_include_or_exclude(self):
-        """ no include or exclude """
+        """no include or exclude"""
 
         # Add all of the eggs in the egg basket.
         self._add_eggs_on_path([self.egg_dir])
@@ -48,7 +48,7 @@ def test_no_include_or_exclude(self):
         self.assertTrue("acme.baz" in ids)
 
     def test_include_specific(self):
-        """ include specific """
+        """include specific"""
         # Add all of the eggs in the egg basket.
         self._add_eggs_on_path([self.egg_dir])
 
@@ -69,7 +69,7 @@ def test_include_specific(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_include_multiple(self):
-        """ include multiple """
+        """include multiple"""
 
         # Add all of the eggs in the egg basket.
         self._add_eggs_on_path([self.egg_dir])
@@ -91,7 +91,7 @@ def test_include_multiple(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_exclude_specific(self):
-        """ exclude specific """
+        """exclude specific"""
 
         # Add all of the eggs in the egg basket.
         self._add_eggs_on_path([self.egg_dir])
@@ -116,7 +116,7 @@ def test_exclude_specific(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_exclude_multiple(self):
-        """ exclude multiple """
+        """exclude multiple"""
 
         # Add all of the eggs in the egg basket.
         self._add_eggs_on_path([self.egg_dir])
@@ -162,8 +162,8 @@ def test_uses_global_working_set_by_default(self):
     ###########################################################################
 
     def _test_start_and_stop(self, plugin_manager, expected):
-        """ Make sure the plugin manager starts and stops the expected plugins.
-
+        """
+        Make sure the plugin manager starts and stops the expected plugins.
         """
 
         # Make sure the plugin manager found only the required plugins.
diff --git a/envisage/tests/test_extension_point.py b/envisage/tests/test_extension_point.py
index a339286b3..c078e3c70 100644
--- a/envisage/tests/test_extension_point.py
+++ b/envisage/tests/test_extension_point.py
@@ -12,23 +12,23 @@
 # Standard library imports.
 import unittest
 
-# Enthought library imports.
-from envisage.api import Application, ExtensionPoint
-from envisage.api import ExtensionRegistry
 from traits.api import HasTraits, Int, List, TraitError
 
+# Enthought library imports.
+from envisage.api import Application, ExtensionPoint, ExtensionRegistry
+
 
 class HasExtensionPoints(HasTraits):
-    """ Base class for all test classes that use the 'ExtensionPoint' type. """
+    """Base class for all test classes that use the 'ExtensionPoint' type."""
 
     extension_registry = None
 
 
 class ExtensionPointTestCase(unittest.TestCase):
-    """ Tests for extension points. """
+    """Tests for extension points."""
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         # We do all of the testing via the application to make sure it offers
         # the same interface!
@@ -38,7 +38,7 @@ def setUp(self):
         HasExtensionPoints.extension_registry = self.registry
 
     def test_invalid_extension_point_type(self):
-        """ invalid extension point type """
+        """invalid extension point type"""
 
         # Extension points currently have to be 'List's of something! The
         # default is a list of anything.
@@ -46,7 +46,7 @@ def test_invalid_extension_point_type(self):
             ExtensionPoint(Int, "my.ep")
 
     def test_no_reference_to_extension_registry(self):
-        """ no reference to extension registry """
+        """no reference to extension registry"""
 
         registry = self.registry
 
@@ -67,7 +67,7 @@ class Foo(HasTraits):
             getattr(f, "x")
 
     def test_extension_point_changed(self):
-        """ extension point changed """
+        """extension point changed"""
 
         registry = self.registry
 
@@ -79,7 +79,7 @@ class Foo(HasExtensionPoints):
             x = ExtensionPoint(id="my.ep")
 
             def _x_changed(self):
-                """ Static trait change handler. """
+                """Static trait change handler."""
 
                 self.x_changed_called = True
 
@@ -112,7 +112,7 @@ def _x_changed(self):
         self.assertEqual(False, f.x_changed_called)
 
     def test_mutate_extension_point_no_effect(self):
-        """ Extension point is recomputed so mutation has no effect. """
+        """Extension point is recomputed so mutation has no effect."""
 
         registry = self.registry
 
@@ -137,7 +137,7 @@ class Foo(HasExtensionPoints):
         self.assertEqual(f.x, [1, 2, 3])
 
     def test_untyped_extension_point(self):
-        """ untyped extension point """
+        """untyped extension point"""
 
         registry = self.registry
 
@@ -161,7 +161,7 @@ class Foo(HasExtensionPoints):
         self.assertEqual([42, "a string", True], g.x)
 
     def test_typed_extension_point(self):
-        """ typed extension point """
+        """typed extension point"""
 
         registry = self.registry
 
@@ -185,7 +185,7 @@ class Foo(HasExtensionPoints):
         self.assertEqual([42, 43, 44], g.x)
 
     def test_invalid_extension_point(self):
-        """ invalid extension point """
+        """invalid extension point"""
 
         registry = self.registry
 
@@ -206,7 +206,7 @@ class Foo(HasExtensionPoints):
             getattr(f, "x")
 
     def test_extension_point_with_no_id(self):
-        """ extension point with no Id """
+        """extension point with no Id"""
 
         def factory():
             class Foo(HasExtensionPoints):
@@ -216,7 +216,7 @@ class Foo(HasExtensionPoints):
             factory()
 
     def test_set_untyped_extension_point(self):
-        """ set untyped extension point """
+        """set untyped extension point"""
 
         registry = self.registry
 
@@ -235,7 +235,7 @@ class Foo(HasExtensionPoints):
         self.assertEqual([42], registry.get_extensions("my.ep"))
 
     def test_set_typed_extension_point(self):
-        """ set typed extension point """
+        """set typed extension point"""
 
         registry = self.registry
 
@@ -254,7 +254,7 @@ class Foo(HasExtensionPoints):
         self.assertEqual([42], registry.get_extensions("my.ep"))
 
     def test_extension_point_str_representation(self):
-        """ test the string representation of the extension point """
+        """test the string representation of the extension point"""
         ep_repr = "ExtensionPoint(id={!r})"
         ep = self._create_extension_point("my.ep")
         self.assertEqual(ep_repr.format("my.ep"), str(ep))
@@ -265,6 +265,6 @@ def test_extension_point_str_representation(self):
     ###########################################################################
 
     def _create_extension_point(self, id, trait_type=List, desc=""):
-        """ Create an extension point. """
+        """Create an extension point."""
 
         return ExtensionPoint(id=id, trait_type=trait_type, desc=desc)
diff --git a/envisage/tests/test_extension_point_binding.py b/envisage/tests/test_extension_point_binding.py
index eda98ef71..26543e82a 100644
--- a/envisage/tests/test_extension_point_binding.py
+++ b/envisage/tests/test_extension_point_binding.py
@@ -13,11 +13,15 @@
 import unittest
 import weakref
 
-# Enthought library imports.
-from envisage.api import ExtensionPoint
-from envisage.api import bind_extension_point, unbind_extension_point
 from traits.api import Any, HasTraits, List
 
+# Enthought library imports.
+from envisage.api import (
+    bind_extension_point,
+    ExtensionPoint,
+    unbind_extension_point,
+)
+
 # Local imports.
 from envisage.tests.mutable_extension_registry import MutableExtensionRegistry
 
@@ -32,7 +36,7 @@ class BindingTarget(HasTraits):
 
 
 class ExtensionPointBindingTestCase(unittest.TestCase):
-    """ Tests for extension point binding. """
+    """Tests for extension point binding."""
 
     def setUp(self):
         self.extension_registry = MutableExtensionRegistry()
@@ -41,7 +45,7 @@ def tearDown(self):
         del self.extension_registry
 
     def test_untyped_extension_point(self):
-        """ untyped extension point """
+        """untyped extension point"""
 
         registry = self.extension_registry
 
@@ -83,7 +87,7 @@ class Foo(HasTraits):
         self.assertTrue("a string" in event.new.added)
 
     def test_set_extensions_via_trait(self):
-        """ set extensions via trait """
+        """set extensions via trait"""
 
         registry = self.extension_registry
 
@@ -127,7 +131,7 @@ class Foo(HasTraits):
         self.assertTrue("a string" in event.new)
 
     def test_set_extensions_via_registry(self):
-        """ set extensions via registry """
+        """set extensions via registry"""
 
         registry = self.extension_registry
 
@@ -168,7 +172,7 @@ class Foo(HasTraits):
         self.assertTrue("a string" in event.new)
 
     def test_explicit_extension_registry(self):
-        """ explicit extension registry """
+        """explicit extension registry"""
 
         registry = self.extension_registry
 
@@ -195,7 +199,6 @@ class Foo(HasTraits):
         self.assertEqual(0, len(f.x))
 
     def test_should_be_able_to_bind_multiple_traits_on_a_single_object(self):
-
         registry = self.extension_registry
 
         # Add 2 extension points.
@@ -275,6 +278,6 @@ def test_unbinding_removes_references(self):
     ###########################################################################
 
     def _create_extension_point(self, id, trait_type=List, desc=""):
-        """ Create an extension point. """
+        """Create an extension point."""
 
         return ExtensionPoint(id=id, trait_type=trait_type, desc=desc)
diff --git a/envisage/tests/test_extension_point_changed.py b/envisage/tests/test_extension_point_changed.py
index d606fd8d7..c5ed24b4f 100644
--- a/envisage/tests/test_extension_point_changed.py
+++ b/envisage/tests/test_extension_point_changed.py
@@ -14,19 +14,14 @@
 
 # Local imports.
 from envisage.api import ExtensionPointChangedEvent
-from envisage.tests.support import (
-    PluginA,
-    PluginB,
-    PluginC,
-    SimpleApplication,
-)
+from envisage.tests.support import PluginA, PluginB, PluginC, SimpleApplication
 
 
 class ExtensionPointChangedTestCase(unittest.TestCase):
-    """ Tests for the events fired when extension points are changed. """
+    """Tests for the events fired when extension points are changed."""
 
     def test_set_extension_point(self):
-        """ set extension point """
+        """set extension point"""
 
         a = PluginA()
 
@@ -38,7 +33,7 @@ def test_set_extension_point(self):
             setattr(a, "x", [1, 2, 3])
 
     def test_mutate_extension_point_no_events(self):
-        """ Mutation will not emit change event for name_items """
+        """Mutation will not emit change event for name_items"""
 
         events = []
 
@@ -57,7 +52,7 @@ def test_mutate_extension_point_no_events(self):
         self.assertEqual(events, [])
 
     def test_append(self):
-        """ append """
+        """append"""
 
         events = []
 
@@ -102,7 +97,7 @@ def test_append(self):
         self.assertEqual(3, event.new.index)
 
     def test_remove(self):
-        """ remove """
+        """remove"""
 
         events = []
 
@@ -147,7 +142,7 @@ def test_remove(self):
         self.assertEqual(2, event.new.index)
 
     def test_assign_empty_list(self):
-        """ assign empty list """
+        """assign empty list"""
 
         events = []
 
@@ -193,7 +188,7 @@ def test_assign_empty_list(self):
         self.assertEqual(3, event.new.index.stop)
 
     def test_assign_empty_list_no_event(self):
-        """ assign empty list no event """
+        """assign empty list no event"""
 
         events = []
 
@@ -227,7 +222,7 @@ def test_assign_empty_list_no_event(self):
         self.assertEqual(events, [])
 
     def test_assign_non_empty_list(self):
-        """ assign non-empty list """
+        """assign non-empty list"""
 
         events = []
 
@@ -274,9 +269,7 @@ def test_assign_non_empty_list(self):
         self.assertEqual([1, 2, 3], event.new.removed)
 
         # The removed entry should match what the old values say
-        self.assertEqual(
-            event.new.removed, source_values[event.new.index]
-        )
+        self.assertEqual(event.new.removed, source_values[event.new.index])
 
         # If we use the index and apply the changes to the old list, we should
         # recover the new list
@@ -287,7 +280,7 @@ def test_assign_non_empty_list(self):
         self.assertEqual(3, event.new.index.stop)
 
     def test_add_plugin(self):
-        """ add plugin """
+        """add plugin"""
 
         events = []
 
@@ -342,7 +335,7 @@ def test_add_plugin(self):
         self.assertEqual(3, event.new.index)
 
     def test_remove_plugin(self):
-        """ remove plugin """
+        """remove plugin"""
 
         events = []
 
@@ -396,10 +389,13 @@ def test_remove_plugin(self):
         self.assertEqual(0, event.new.index)
 
     def test_extension_point_change_event_str_representation(self):
-        """ test string representation of the ExtensionPointChangedEvent class
         """
-        desired_repr = ("ExtensionPointChangedEvent(extension_point_id={}, "
-                        "index=0, removed=[], added=[])")
+        test string representation of the ExtensionPointChangedEvent class
+        """
+        desired_repr = (
+            "ExtensionPointChangedEvent(extension_point_id={}, "
+            "index=0, removed=[], added=[])"
+        )
         ext_pt_changed_evt = ExtensionPointChangedEvent(extension_point_id=1)
         self.assertEqual(desired_repr.format(1), str(ext_pt_changed_evt))
         self.assertEqual(desired_repr.format(1), repr(ext_pt_changed_evt))
diff --git a/envisage/tests/test_extension_registry.py b/envisage/tests/test_extension_registry.py
index a11e28081..1fa9fc1c9 100644
--- a/envisage/tests/test_extension_registry.py
+++ b/envisage/tests/test_extension_registry.py
@@ -13,28 +13,27 @@
 import contextlib
 import unittest
 
-# Enthought library imports.
-from envisage.api import Application, ExtensionPoint
-from envisage.api import ExtensionRegistry
 from traits.api import List
 
+# Enthought library imports.
+from envisage.api import Application, ExtensionPoint, ExtensionRegistry
 from envisage.tests.test_extension_registry_mixin import (
-    ExtensionRegistryTestMixin
+    ExtensionRegistryTestMixin,
 )
 
 
 class ExtensionRegistryTestCase(ExtensionRegistryTestMixin, unittest.TestCase):
-    """ Tests for the base extension registry. """
+    """Tests for the base extension registry."""
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         # We do all of the testing via the application to make sure it offers
         # the same interface!
         self.registry = Application(extension_registry=ExtensionRegistry())
 
     def test_remove_non_empty_extension_point(self):
-        """ remove non-empty extension point """
+        """remove non-empty extension point"""
 
         registry = self.registry
 
@@ -55,7 +54,7 @@ def test_remove_non_empty_extension_point(self):
         self.assertEqual([], registry.get_extensions("my.ep"))
 
     def test_set_extensions(self):
-        """ set extensions """
+        """set extensions"""
 
         registry = self.registry
 
@@ -75,6 +74,7 @@ def make_function_listener(events):
 
     The listener appends events to the ``events`` list.
     """
+
     def listener(registry, event):
         events.append(event)
 
@@ -85,6 +85,7 @@ class ListensToExtensionPoint:
     """
     Class with a method that can be used as an extension point listener.
     """
+
     def __init__(self, events):
         self.events = events
 
@@ -177,7 +178,8 @@ def assertAppendsTo(self, some_list):
         new_length = len(some_list)
         diff = new_length - old_length
         self.assertEqual(
-            diff, 1,
+            diff,
+            1,
             msg="Expected exactly one new element; got {}".format(diff),
         )
 
@@ -194,6 +196,7 @@ def assertDoesNotModify(self, some_list):
         new_length = len(some_list)
         diff = new_length - old_length
         self.assertEqual(
-            diff, 0,
+            diff,
+            0,
             msg="Expected no new elements; got {}".format(diff),
         )
diff --git a/envisage/tests/test_extension_registry_mixin.py b/envisage/tests/test_extension_registry_mixin.py
index bdfdd85ab..fed1a5e38 100644
--- a/envisage/tests/test_extension_registry_mixin.py
+++ b/envisage/tests/test_extension_registry_mixin.py
@@ -12,21 +12,21 @@
 mixin class.
 """
 
-# Enthought library imports.
-from envisage.api import ExtensionPoint
-from envisage.api import UnknownExtensionPoint
 from traits.api import List
 
+# Enthought library imports.
+from envisage.api import ExtensionPoint, UnknownExtensionPoint
+
 
 class ExtensionRegistryTestMixin:
-    """ Base set of tests for extension registry and its subclasses.
+    """Base set of tests for extension registry and its subclasses.
 
     Test cases inherriting from this mixin should define a setUp method that
     defines self.registry as an instance of ExtensionPointRegistry.
     """
 
     def test_empty_registry(self):
-        """ empty registry """
+        """empty registry"""
 
         registry = self.registry
 
@@ -39,7 +39,7 @@ def test_empty_registry(self):
         self.assertEqual(0, len(extension_points))
 
     def test_add_extension_point(self):
-        """ add extension point """
+        """add extension point"""
 
         registry = self.registry
 
@@ -56,7 +56,7 @@ def test_add_extension_point(self):
         self.assertEqual("my.ep", extension_points[0].id)
 
     def test_get_extension_point(self):
-        """ get extension point """
+        """get extension point"""
 
         registry = self.registry
 
@@ -69,11 +69,11 @@ def test_get_extension_point(self):
         self.assertEqual("my.ep", extension_point.id)
 
     def test_get_extension_point_return_none_if_not_found(self):
-        """ get extension point return None if id is not found. """
+        """get extension point return None if id is not found."""
         self.assertIsNone(self.registry.get_extension_point("i.do.not.exist"))
 
     def test_get_extensions_mutation_no_effect_if_undefined(self):
-        """ test one cannot mutate the registry by mutating the list. """
+        """test one cannot mutate the registry by mutating the list."""
         # The extension point with id "my.ep" has not been defined
         extensions = self.registry.get_extensions("my.ep")
 
@@ -85,7 +85,7 @@ def test_get_extensions_mutation_no_effect_if_undefined(self):
         self.assertEqual(self.registry.get_extensions("my.ep"), [])
 
     def test_remove_empty_extension_point(self):
-        """ remove empty_extension point """
+        """remove empty_extension point"""
 
         registry = self.registry
 
@@ -100,7 +100,7 @@ def test_remove_empty_extension_point(self):
         self.assertEqual(0, len(extension_points))
 
     def test_remove_non_existent_extension_point(self):
-        """ remove non existent extension point """
+        """remove non existent extension point"""
 
         registry = self.registry
 
@@ -108,12 +108,12 @@ def test_remove_non_existent_extension_point(self):
             registry.remove_extension_point("my.ep")
 
     def test_remove_non_existent_listener(self):
-        """ remove non existent listener """
+        """remove non existent listener"""
 
         registry = self.registry
 
         def listener(registry, extension_point, added, removed, index):
-            """ Called when an extension point has changed. """
+            """Called when an extension point has changed."""
 
             self.listener_called = (registry, extension_point, added, removed)
 
@@ -121,6 +121,6 @@ def listener(registry, extension_point, added, removed, index):
             registry.remove_extension_point_listener(listener)
 
     def create_extension_point(self, id, trait_type=List, desc=""):
-        """ Create an extension point. """
+        """Create an extension point."""
 
         return ExtensionPoint(id=id, trait_type=trait_type, desc=desc)
diff --git a/envisage/tests/test_ids.py b/envisage/tests/test_ids.py
index 71bb8c32b..40d2cc612 100644
--- a/envisage/tests/test_ids.py
+++ b/envisage/tests/test_ids.py
@@ -57,6 +57,5 @@ def check_id_against_plugin(self, id_string, plugin_klass):
             The Plugin subclass to check.
         """
         self.assertEqual(
-            getattr(envisage.ids, id_string),
-            getattr(plugin_klass, id_string)
+            getattr(envisage.ids, id_string), getattr(plugin_klass, id_string)
         )
diff --git a/envisage/tests/test_import_manager.py b/envisage/tests/test_import_manager.py
index 55e7724d6..4ef9f7f60 100644
--- a/envisage/tests/test_import_manager.py
+++ b/envisage/tests/test_import_manager.py
@@ -17,17 +17,17 @@
 
 
 class ImportManagerTestCase(unittest.TestCase):
-    """ Tests for the import manager. """
+    """Tests for the import manager."""
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         # We do all of the testing via the application to make sure it offers
         # the same interface!
         self.import_manager = Application(import_manager=ImportManager())
 
     def test_import_dotted_symbol(self):
-        """ import dotted symbol """
+        """import dotted symbol"""
 
         import tarfile
 
@@ -35,7 +35,7 @@ def test_import_dotted_symbol(self):
         self.assertEqual(symbol, tarfile.TarFile)
 
     def test_import_nested_symbol(self):
-        """ import nested symbol """
+        """import nested symbol"""
 
         import tarfile
 
@@ -43,7 +43,7 @@ def test_import_nested_symbol(self):
         self.assertEqual(symbol, tarfile.TarFile.open)
 
     def test_import_dotted_module(self):
-        """ import dotted module """
+        """import dotted module"""
 
         symbol = self.import_manager.import_symbol(
             "envisage.api:ImportManager"
diff --git a/envisage/tests/test_package_plugin_manager.py b/envisage/tests/test_package_plugin_manager.py
index 406bf38e3..5b1d8ad39 100644
--- a/envisage/tests/test_package_plugin_manager.py
+++ b/envisage/tests/test_package_plugin_manager.py
@@ -10,23 +10,22 @@
 """ Tests for the 'Package' plugin manager. """
 
 
-from os.path import dirname, join
 import unittest
+from os.path import dirname, join
 
 from envisage.package_plugin_manager import PackagePluginManager
 
 
 class PackagePluginManagerTestCase(unittest.TestCase):
-    """ Tests for the 'Package' plugin manager. """
+    """Tests for the 'Package' plugin manager."""
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         # The location of the 'plugins' test data directory.
         self.plugins_dir = join(dirname(__file__), "plugins")
 
     def test_find_plugins_in_packages_on_the_plugin_path(self):
-
         with self.assertWarns(DeprecationWarning):
             plugin_manager = PackagePluginManager(
                 plugin_path=[self.plugins_dir]
@@ -39,7 +38,6 @@ def test_find_plugins_in_packages_on_the_plugin_path(self):
         self.assertIn("pear", ids)
 
     def test_only_find_plugins_whose_ids_are_in_the_include_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         include = ["orange", "pear"]
@@ -57,7 +55,6 @@ def test_only_find_plugins_whose_ids_are_in_the_include_list(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_only_find_plugins_matching_a_wildcard_in_the_include_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         include = ["*r*"]
@@ -75,7 +72,6 @@ def test_only_find_plugins_matching_a_wildcard_in_the_include_list(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_ignore_plugins_whose_ids_are_in_the_exclude_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         exclude = ["orange", "pear"]
@@ -93,7 +89,6 @@ def test_ignore_plugins_whose_ids_are_in_the_exclude_list(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_ignore_plugins_matching_a_wildcard_in_the_exclude_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         exclude = ["*r*"]
@@ -130,8 +125,8 @@ def test_reflect_changes_to_the_plugin_path(self):
     #### Private protocol #####################################################
 
     def _test_start_and_stop(self, plugin_manager, expected):
-        """ Make sure the plugin manager starts and stops the expected plugins.
-
+        """
+        Make sure the plugin manager starts and stops the expected plugins.
         """
 
         # Make sure the plugin manager found only the required plugins.
diff --git a/envisage/tests/test_plugin.py b/envisage/tests/test_plugin.py
index 36ef19fd2..01604999f 100644
--- a/envisage/tests/test_plugin.py
+++ b/envisage/tests/test_plugin.py
@@ -10,16 +10,17 @@
 """ Tests for plugins. """
 
 
+import unittest
+
 # Standard library imports.
 from os.path import exists, join
-import unittest
+
+from traits.api import HasTraits, Instance, Int, Interface, List, provides
 
 # Enthought library imports.
-from envisage.api import Application, ExtensionPoint
-from envisage.api import IPluginActivator, Plugin
+from envisage.api import Application, ExtensionPoint, IPluginActivator, Plugin
 from envisage.tests.ets_config_patcher import ETSConfigPatcher
 from envisage.tests.support import SimpleApplication
-from traits.api import HasTraits, Instance, Int, Interface, List, provides
 
 
 class TestPlugin(Plugin):
@@ -27,7 +28,7 @@ class TestPlugin(Plugin):
 
 
 class PluginTestCase(unittest.TestCase):
-    """ Tests for plugins. """
+    """Tests for plugins."""
 
     def setUp(self):
         ets_config_patcher = ETSConfigPatcher()
@@ -35,7 +36,7 @@ def setUp(self):
         self.addCleanup(ets_config_patcher.stop)
 
     def test_id_policy(self):
-        """ id policy """
+        """id policy"""
 
         # If no Id is specified then use 'module_name.class_name'.
         p = Plugin()
@@ -51,7 +52,7 @@ def test_id_policy(self):
         self.assertEqual("fred", p.name)
 
     def test_name_policy(self):
-        """ name policy """
+        """name policy"""
 
         # If name is specified then use the plugin's class name.
         p = Plugin()
@@ -69,19 +70,19 @@ class ThisIsMyPlugin(Plugin):
         self.assertEqual("This Is My Plugin", p.name)
 
     def test_plugin_activator(self):
-        """ plugin activator. """
+        """plugin activator."""
 
         @provides(IPluginActivator)
         class NullPluginActivator(HasTraits):
-            """ A plugin activator that does nothing! """
+            """A plugin activator that does nothing!"""
 
             def start_plugin(self, plugin):
-                """ Start a plugin. """
+                """Start a plugin."""
 
                 self.started = plugin
 
             def stop_plugin(self, plugin):
-                """ Stop a plugin. """
+                """Stop a plugin."""
 
                 self.stopped = plugin
 
@@ -109,7 +110,7 @@ class PluginB(Plugin):
         self.assertEqual(a, plugin_activator.stopped)
 
     def test_service(self):
-        """ service """
+        """service"""
 
         class Foo(HasTraits):
             pass
@@ -149,7 +150,7 @@ class PluginA(Plugin):
         self.assertEqual(None, application.get_service(Baz))
 
     def test_service_protocol(self):
-        """ service protocol """
+        """service protocol"""
 
         class IFoo(Interface):
             pass
@@ -180,7 +181,7 @@ class PluginA(Plugin):
         self.assertEqual(None, application.get_service(IBar))
 
     def test_multiple_trait_contributions(self):
-        """ multiple trait contributions """
+        """multiple trait contributions"""
 
         class PluginA(Plugin):
             id = "A"
@@ -203,7 +204,7 @@ class PluginB(Plugin):
             application.get_extensions("x")
 
     def test_exception_in_trait_contribution(self):
-        """ exception in trait contribution """
+        """exception in trait contribution"""
 
         class PluginA(Plugin):
             id = "A"
@@ -215,7 +216,7 @@ class PluginB(Plugin):
             x = List(contributes_to="x")
 
             def _x_default(self):
-                """ Trait initializer. """
+                """Trait initializer."""
 
                 raise 1 / 0
 
@@ -230,7 +231,7 @@ def _x_default(self):
             application.get_extensions("x")
 
     def test_contributes_to(self):
-        """ contributes to """
+        """contributes to"""
 
         class PluginA(Plugin):
             id = "A"
@@ -250,7 +251,7 @@ class PluginB(Plugin):
         self.assertEqual([1, 2, 3], application.get_extensions("x"))
 
     def test_add_plugins_to_empty_application(self):
-        """ add plugins to empty application """
+        """add plugins to empty application"""
 
         class PluginA(Plugin):
             id = "A"
@@ -326,7 +327,7 @@ class PluginC(Plugin):
         self.assertEqual([4, 5, 6], a.removed)
 
     def test_home(self):
-        """ home """
+        """home"""
 
         class PluginA(Plugin):
             id = "A"
@@ -363,7 +364,7 @@ class PluginB(Plugin):
         self.assertTrue(exists(b.home))
 
     def test_no_recursion(self):
-        """ Regression test for #119. """
+        """Regression test for #119."""
 
         class PluginA(Plugin):
             id = "A"
@@ -373,7 +374,7 @@ class PluginA(Plugin):
         application.get_extensions("bob")
 
     def test_plugin_str_representation(self):
-        """ test the string representation of the plugin """
+        """test the string representation of the plugin"""
         plugin_repr = "TestPlugin(id={!r}, name={!r})"
         plugin = TestPlugin(id="Fred", name="Wilma")
         self.assertEqual(str(plugin), plugin_repr.format("Fred", "Wilma"))
diff --git a/envisage/tests/test_plugin_manager.py b/envisage/tests/test_plugin_manager.py
index e3615bb60..cc0cb1e1b 100644
--- a/envisage/tests/test_plugin_manager.py
+++ b/envisage/tests/test_plugin_manager.py
@@ -13,13 +13,14 @@
 # Standard library imports.
 import unittest
 
+from traits.api import Bool
+
 # Enthought library imports.
 from envisage.api import Plugin, PluginManager
-from traits.api import Bool
 
 
 class SimplePlugin(Plugin):
-    """ A simple plugin. """
+    """A simple plugin."""
 
     #### 'SimplePlugin' interface #############################################
 
@@ -31,41 +32,41 @@ class SimplePlugin(Plugin):
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         self.started = True
         self.stopped = False
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         self.started = False
         self.stopped = True
 
 
 class BadPlugin(Plugin):
-    """ A plugin that just causes trouble ;^). """
+    """A plugin that just causes trouble ;^)."""
 
     ###########################################################################
     # 'IPlugin' interface.
     ###########################################################################
 
     def start(self):
-        """ Start the plugin. """
+        """Start the plugin."""
 
         raise 1 / 0
 
     def stop(self):
-        """ Stop the plugin. """
+        """Stop the plugin."""
 
         raise 1 / 0
 
 
 class PluginManagerTestCase(unittest.TestCase):
-    """ Tests for the plugin manager. """
+    """Tests for the plugin manager."""
 
     def test_get_plugin(self):
-        """ get plugin """
+        """get plugin"""
 
         simple_plugin = SimplePlugin()
         plugin_manager = PluginManager(plugins=[simple_plugin])
@@ -78,7 +79,7 @@ def test_get_plugin(self):
         self.assertEqual(None, plugin_manager.get_plugin("bogus"))
 
     def test_iteration_over_plugins(self):
-        """ iteration over plugins """
+        """iteration over plugins"""
 
         simple_plugin = SimplePlugin()
         bad_plugin = BadPlugin()
@@ -93,7 +94,7 @@ def test_iteration_over_plugins(self):
         self.assertEqual([simple_plugin, bad_plugin], plugins)
 
     def test_start_and_stop(self):
-        """ start and stop """
+        """start and stop"""
 
         simple_plugin = SimplePlugin()
         plugin_manager = PluginManager(plugins=[simple_plugin])
@@ -113,7 +114,7 @@ def test_start_and_stop(self):
         self.assertEqual(True, simple_plugin.stopped)
 
     def test_start_and_stop_errors(self):
-        """ start and stop errors """
+        """start and stop errors"""
 
         simple_plugin = SimplePlugin()
         bad_plugin = BadPlugin()
@@ -138,7 +139,6 @@ def test_start_and_stop_errors(self):
             plugin_manager.stop_plugin(plugin_id="bogus")
 
     def test_only_include_plugins_whose_ids_are_in_the_include_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         include = ["foo", "bar"]
@@ -163,7 +163,6 @@ def test_only_include_plugins_whose_ids_are_in_the_include_list(self):
     def test_only_include_plugins_matching_a_wildcard_in_the_include_list(
         self,
     ):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         include = ["b*"]
@@ -186,7 +185,6 @@ def test_only_include_plugins_matching_a_wildcard_in_the_include_list(
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_ignore_plugins_whose_ids_are_in_the_exclude_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         exclude = ["foo", "baz"]
@@ -209,7 +207,6 @@ def test_ignore_plugins_whose_ids_are_in_the_exclude_list(self):
         self._test_start_and_stop(plugin_manager, expected)
 
     def test_ignore_plugins_matching_a_wildcard_in_the_exclude_list(self):
-
         # Note that the items in the list use the 'fnmatch' syntax for matching
         # plugins Ids.
         exclude = ["b*"]
@@ -234,8 +231,8 @@ def test_ignore_plugins_matching_a_wildcard_in_the_exclude_list(self):
     #### Private protocol #####################################################
 
     def _test_start_and_stop(self, plugin_manager, expected):
-        """ Make sure the plugin manager starts and stops the expected plugins.
-
+        """
+        Make sure the plugin manager starts and stops the expected plugins.
         """
 
         # Make sure the plugin manager found only the required plugins.
diff --git a/envisage/tests/test_provider_extension_registry.py b/envisage/tests/test_provider_extension_registry.py
index 6635a3d2c..69c32221a 100644
--- a/envisage/tests/test_provider_extension_registry.py
+++ b/envisage/tests/test_provider_extension_registry.py
@@ -12,43 +12,48 @@
 # Standard library imports.
 import unittest
 
-# Enthought library imports.
-from envisage.api import ExtensionPoint, ExtensionProvider
-from envisage.api import ProviderExtensionRegistry
 from traits.api import Int, List
 
+# Enthought library imports.
+from envisage.api import (
+    ExtensionPoint,
+    ExtensionProvider,
+    ProviderExtensionRegistry,
+)
+
 # Local imports.
 from envisage.tests.test_extension_registry_mixin import (
-    ExtensionRegistryTestMixin
+    ExtensionRegistryTestMixin,
 )
 
 
 class ProviderExtensionRegistryTestCase(
-        ExtensionRegistryTestMixin, unittest.TestCase):
-    """ Tests for the provider extension registry. """
+    ExtensionRegistryTestMixin, unittest.TestCase
+):
+    """Tests for the provider extension registry."""
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         self.registry = ProviderExtensionRegistry()
 
     def test_providers(self):
-        """ providers """
+        """providers"""
 
         registry = self.registry
 
         # Some providers.
         class ProviderA(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             def get_extension_points(self):
-                """ Return the extension points offered by the provider. """
+                """Return the extension points offered by the provider."""
 
                 return [ExtensionPoint(List, "x")]
 
             def get_extensions(self, extension_point):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point == "x":
@@ -60,11 +65,11 @@ def get_extensions(self, extension_point):
                 return extensions
 
         class ProviderB(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             def get_extensions(self, extension_point):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point == "x":
@@ -76,7 +81,7 @@ def get_extensions(self, extension_point):
                 return extensions
 
         class ProviderC(ExtensionProvider):
-            """ An empty provider! """
+            """An empty provider!"""
 
         # Add the providers to the registry.
         registry.add_provider(ProviderA())
@@ -94,24 +99,24 @@ class ProviderC(ExtensionProvider):
         self.assertEqual("x", extension_points[0].id)
 
     def test_provider_extensions_changed(self):
-        """ provider extensions changed """
+        """provider extensions changed"""
 
         registry = self.registry
 
         # Some providers.
         class ProviderA(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             x = List(Int)
 
             def get_extension_points(self):
-                """ Return the extension points offered by the provider. """
+                """Return the extension points offered by the provider."""
 
                 return [ExtensionPoint(List, "my.ep")]
 
             def get_extensions(self, extension_point_id):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point_id == "my.ep":
@@ -123,27 +128,27 @@ def get_extensions(self, extension_point_id):
                 return extensions
 
             def _x_changed(self, old, new):
-                """ Static trait change handler. """
+                """Static trait change handler."""
 
                 self._fire_extension_point_changed(
                     "my.ep", new, old, slice(0, len(old))
                 )
 
             def _x_items_changed(self, event):
-                """ Static trait change handler. """
+                """Static trait change handler."""
 
                 self._fire_extension_point_changed(
                     "my.ep", event.added, event.removed, event.index
                 )
 
         class ProviderB(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             x = List(Int)
 
             def get_extensions(self, extension_point_id):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point_id == "my.ep":
@@ -155,14 +160,14 @@ def get_extensions(self, extension_point_id):
                 return extensions
 
             def _x_changed(self, old, new):
-                """ Static trait change handler. """
+                """Static trait change handler."""
 
                 self._fire_extension_point_changed(
                     "my.ep", new, old, slice(0, len(old))
                 )
 
             def _x_items_changed(self, event):
-                """ Static trait change handler. """
+                """Static trait change handler."""
 
                 self._fire_extension_point_changed(
                     "my.ep", event.added, event.removed, event.index
@@ -181,7 +186,7 @@ def _x_items_changed(self, event):
 
         # Add an extension listener to the registry.
         def listener(registry, event):
-            """ A useful trait change handler for testing! """
+            """A useful trait change handler for testing!"""
 
             listener.registry = registry
             listener.extension_point = event.extension_point_id
@@ -235,22 +240,22 @@ def listener(registry, event):
         self.assertEqual([42, 43, 1, 2], extensions)
 
     def test_add_provider(self):
-        """ add provider """
+        """add provider"""
 
         registry = self.registry
 
         # A provider.
         class ProviderA(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             def get_extension_points(self):
-                """ Return the extension points offered by the provider. """
+                """Return the extension points offered by the provider."""
 
                 return [ExtensionPoint(List, "x")]
 
             def get_extensions(self, extension_point):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point == "x":
@@ -262,7 +267,7 @@ def get_extensions(self, extension_point):
                 return extensions
 
             def _x_items_changed(self, event):
-                """ Static trait change handler. """
+                """Static trait change handler."""
 
                 self._fire_extension_point_changed(
                     "x", event.added, event.removed, event.index
@@ -278,7 +283,7 @@ def _x_items_changed(self, event):
 
         # Add an extension listener to the registry.
         def listener(registry, event):
-            """ A useful trait change handler for testing! """
+            """A useful trait change handler for testing!"""
 
             listener.registry = registry
             listener.extension_point = event.extension_point_id
@@ -290,11 +295,11 @@ def listener(registry, event):
 
         # Add a new provider.
         class ProviderB(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             def get_extensions(self, extension_point):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point == "x":
@@ -320,16 +325,16 @@ def get_extensions(self, extension_point):
         self.assertTrue(44 in extensions)
 
     def test_get_providers(self):
-        """ get providers """
+        """get providers"""
 
         registry = self.registry
 
         # Some providers.
         class ProviderA(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
         class ProviderB(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
         a = ProviderA()
         b = ProviderB()
@@ -342,22 +347,22 @@ class ProviderB(ExtensionProvider):
         self.assertEqual([a, b], registry.get_providers())
 
     def test_remove_provider(self):
-        """ remove provider """
+        """remove provider"""
 
         registry = self.registry
 
         # Some providers.
         class ProviderA(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             def get_extension_points(self):
-                """ Return the extension points offered by the provider. """
+                """Return the extension points offered by the provider."""
 
                 return [ExtensionPoint(List, "x"), ExtensionPoint(List, "y")]
 
             def get_extensions(self, extension_point):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point == "x":
@@ -369,18 +374,18 @@ def get_extensions(self, extension_point):
                 return extensions
 
             def _x_items_changed(self, event):
-                """ Static trait change handler. """
+                """Static trait change handler."""
 
                 self._fire_extension_point_changed(
                     "x", event.added, event.removed, event.index
                 )
 
         class ProviderB(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             def get_extensions(self, extension_point):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point == "x":
@@ -406,7 +411,7 @@ def get_extensions(self, extension_point):
 
         # Add an extension listener to the registry.
         def listener(registry, event):
-            """ A useful trait change handler for testing! """
+            """A useful trait change handler for testing!"""
 
             listener.registry = registry
             listener.extension_point = event.extension_point_id
@@ -444,22 +449,22 @@ def listener(registry, event):
         self.assertEqual([42], listener.removed)
 
     def test_remove_provider_with_no_contributions(self):
-        """ remove provider with no contributions """
+        """remove provider with no contributions"""
 
         registry = self.registry
 
         # Some providers.
         class ProviderA(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             def get_extension_points(self):
-                """ Return the extension points offered by the provider. """
+                """Return the extension points offered by the provider."""
 
                 return [ExtensionPoint(List, "x"), ExtensionPoint(List, "y")]
 
             def get_extensions(self, extension_point):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 return []
@@ -474,7 +479,7 @@ def get_extensions(self, extension_point):
 
         # Add an extension listener to the registry.
         def listener(registry, event):
-            """ A useful trait change handler for testing! """
+            """A useful trait change handler for testing!"""
 
             listener.registry = registry
             listener.extension_point = event.extension_point_id
@@ -498,13 +503,13 @@ def listener(registry, event):
         self.assertEqual(None, getattr(listener, "registry", None))
 
     def test_remove_non_existent_provider(self):
-        """ remove provider """
+        """remove provider"""
 
         registry = self.registry
 
         # Some providers.
         class ProviderA(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             pass
 
@@ -515,7 +520,7 @@ class ProviderA(ExtensionProvider):
             registry.remove_provider(a)
 
     def test_set_extensions(self):
-        """ set extensions """
+        """set extensions"""
 
         registry = self.registry
 
@@ -527,22 +532,24 @@ def test_set_extensions(self):
             registry.set_extensions("my.ep", [1, 2, 3])
 
     def test_remove_non_empty_extension_point(self):
-        """ remove non-empty extension point """
+        """remove non-empty extension point"""
 
         registry = self.registry
 
         # Some providers.
         class ProviderA(ExtensionProvider):
-            """ An extension provider. """
+            """An extension provider."""
 
             def get_extension_points(self):
-                """ Return the extension points offered by the provider. """
+                """
+                Return the extension points offered by the provider.
+                """
 
                 return [ExtensionPoint(List, "x")]
 
             def get_extensions(self, extension_point):
-                """ Return the provider's contributions to an extension point.
-
+                """
+                Return the provider's contributions to an extension point.
                 """
 
                 if extension_point == "x":
diff --git a/envisage/tests/test_service.py b/envisage/tests/test_service.py
index 84c8f7d0b..f43140c3d 100644
--- a/envisage/tests/test_service.py
+++ b/envisage/tests/test_service.py
@@ -20,10 +20,10 @@
 
 
 class ServiceTestCase(unittest.TestCase):
-    """ Tests for the 'Service' trait type. """
+    """Tests for the 'Service' trait type."""
 
     def test_service_trait_type(self):
-        """ service trait type"""
+        """service trait type"""
 
         class Foo(HasTraits):
             pass
@@ -56,7 +56,7 @@ class PluginB(Plugin):
             setattr(b, "foo", "bogus")
 
     def test_service_trait_type_with_no_service_registry(self):
-        """ service trait type with no service registry """
+        """service trait type with no service registry"""
 
         class Foo(HasTraits):
             pass
@@ -71,7 +71,7 @@ class Bar(HasTraits):
             getattr(b, "foo")
 
     def test_service_str_representation(self):
-        """ test the string representation of the service """
+        """test the string representation of the service"""
 
         class Foo(HasTraits):
             pass
diff --git a/envisage/tests/test_service_registry.py b/envisage/tests/test_service_registry.py
index 17b62148b..5b53bc71f 100644
--- a/envisage/tests/test_service_registry.py
+++ b/envisage/tests/test_service_registry.py
@@ -14,30 +14,30 @@
 import sys
 import unittest
 
-# Enthought library imports.
-from envisage.api import Application, ServiceRegistry, NoSuchServiceError
 from traits.api import HasTraits, Int, Interface, provides
 
+# Enthought library imports.
+from envisage.api import Application, NoSuchServiceError, ServiceRegistry
 
 # This module's package.
 PKG = "envisage.tests"
 
 
 def service_factory(**properties):
-    """ A factory for foos. """
+    """A factory for foos."""
 
     return HasTraits(**properties)
 
 
 class ServiceRegistryTestCase(unittest.TestCase):
-    """ Tests for the service registry. """
+    """Tests for the service registry."""
 
     ###########################################################################
     # 'TestCase' interface.
     ###########################################################################
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         # We do all of the testing via the application to make sure it offers
         # the same interface!
@@ -72,7 +72,7 @@ class IFoo(Interface):
             self.service_registry.get_required_service(IFoo)
 
     def test_imported_service_factory(self):
-        """ imported service factory """
+        """imported service factory"""
 
         class IFoo(Interface):
             price = Int
@@ -98,7 +98,7 @@ class IFoo(Interface):
         self.assertTrue(service is service2)
 
     def test_function_service_factory(self):
-        """ function service factory """
+        """function service factory"""
 
         class IFoo(Interface):
             price = Int
@@ -108,7 +108,7 @@ class Foo(HasTraits):
             price = Int
 
         def foo_factory(**properties):
-            """ A factory for foos. """
+            """A factory for foos."""
 
             return Foo(**properties)
 
@@ -128,11 +128,11 @@ def foo_factory(**properties):
         self.assertTrue(service is service2)
 
     def test_lazy_function_service_factory(self):
-        """ lazy function service factory """
+        """lazy function service factory"""
 
         # Register a service factory by name.
         def foo_factory(**properties):
-            """ A factory for foos. """
+            """A factory for foos."""
 
             from envisage.tests.foo import Foo
 
@@ -167,13 +167,13 @@ def foo_factory(**properties):
         del sys.modules[foo]
 
     def test_lazy_bound_method_service_factory(self):
-        """ lazy bound method service factory """
+        """lazy bound method service factory"""
 
         i_foo = PKG + ".i_foo.IFoo"
         foo = PKG + ".foo"
 
         class ServiceProvider(HasTraits):
-            """ A class that provides a service.
+            """A class that provides a service.
 
             This is used to make sure a bound method can be used as a service
             factory.
@@ -182,7 +182,7 @@ class ServiceProvider(HasTraits):
 
             # Register a service factory by name.
             def foo_factory(self, **properties):
-                """ A factory for foos. """
+                """A factory for foos."""
 
                 from envisage.tests.foo import Foo
 
@@ -215,7 +215,7 @@ def foo_factory(self, **properties):
         del sys.modules[foo]
 
     def test_get_services(self):
-        """ get services """
+        """get services"""
 
         class IFoo(Interface):
             pass
@@ -243,7 +243,7 @@ class IBar(Interface):
         self.assertEqual([], services)
 
     def test_get_services_with_strings(self):
-        """ get services with strings """
+        """get services with strings"""
 
         from envisage.tests.foo import Foo
 
@@ -258,7 +258,7 @@ def test_get_services_with_strings(self):
         self.assertEqual(2, len(services))
 
     def test_get_services_with_query(self):
-        """ get services with query """
+        """get services with query"""
 
         class IFoo(Interface):
             price = Int
@@ -301,7 +301,7 @@ class IBar(Interface):
         self.assertEqual([], services)
 
     def test_get_service(self):
-        """ get service """
+        """get service"""
 
         class IFoo(Interface):
             pass
@@ -329,7 +329,7 @@ class IBar(Interface):
         self.assertEqual(None, service)
 
     def test_get_service_with_query(self):
-        """ get service with query """
+        """get service with query"""
 
         class IFoo(Interface):
             price = Int
@@ -370,7 +370,7 @@ class IBar(Interface):
         self.assertEqual(None, service)
 
     def test_get_and_set_service_properties(self):
-        """ get and set service properties """
+        """get and set service properties"""
 
         class IFoo(Interface):
             price = Int
@@ -422,7 +422,7 @@ class Foo(HasTraits):
             self.service_registry.set_service_properties(-1, {})
 
     def test_unregister_service(self):
-        """ unregister service """
+        """unregister service"""
 
         class IFoo(Interface):
             price = Int
@@ -478,7 +478,7 @@ class Foo(HasTraits):
             self.service_registry.unregister_service(-1)
 
     def test_minimize_and_maximize(self):
-        """ minimize and maximize """
+        """minimize and maximize"""
 
         class IFoo(Interface):
             price = Int
diff --git a/envisage/tests/test_slice.py b/envisage/tests/test_slice.py
index 5365953e0..04bcf20c8 100644
--- a/envisage/tests/test_slice.py
+++ b/envisage/tests/test_slice.py
@@ -20,13 +20,12 @@
 # Enthought library imports.
 from traits.api import HasTraits, List
 
-
 # The starting list for all tests.
 TEST_LIST = [7, 9, 2, 3, 4, 1, 6, 5, 8, 0]
 
 
 def listener(obj, trait_name, old, event):
-    """ Recreate a list operation from a trait list event. """
+    """Recreate a list operation from a trait list event."""
 
     clone = TEST_LIST[:]
 
@@ -47,7 +46,7 @@ def listener(obj, trait_name, old, event):
             # workaroud for traits bug in Python 3
             # https://github.com/enthought/traits/issues/334
             index = event.index if event.index is not None else 0
-            del clone[index:index + len(event.removed)]
+            del clone[index : index + len(event.removed)]
 
     # If nothing was removed then it is an 'append', 'insert' or 'extend'
     # operation.
@@ -56,7 +55,7 @@ def listener(obj, trait_name, old, event):
             clone[event.index] = added
 
         else:
-            clone[event.index:event.index] = added
+            clone[event.index : event.index] = added
 
     # Otherwise, it is an assigment ('sort' and 'reverse' fall into this
     # category).
@@ -65,16 +64,16 @@ def listener(obj, trait_name, old, event):
             clone[event.index] = added
 
         else:
-            clone[event.index:event.index + len(added)] = added
+            clone[event.index : event.index + len(added)] = added
 
     listener.clone = clone
 
 
 class SliceTestCase(unittest.TestCase):
-    """ Tests to help find out how trait list events work. """
+    """Tests to help find out how trait list events work."""
 
     def setUp(self):
-        """ Prepares the test fixture before each test method is called. """
+        """Prepares the test fixture before each test method is called."""
 
         class Foo(HasTraits):
             elts = List
@@ -83,98 +82,98 @@ class Foo(HasTraits):
         self.f.on_trait_change(listener, "elts_items")
 
     def test_append(self):
-        """ append """
+        """append"""
 
         self.f.elts.append(99)
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_insert(self):
-        """ insert """
+        """insert"""
 
         self.f.elts.insert(3, 99)
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_extend(self):
-        """ extend """
+        """extend"""
 
         self.f.elts.extend([99, 100])
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_remove(self):
-        """ remove """
+        """remove"""
 
         self.f.elts.remove(5)
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_reverse(self):
-        """ reverse """
+        """reverse"""
 
         self.f.elts.reverse()
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_sort(self):
-        """ sort """
+        """sort"""
 
         self.f.elts.sort()
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_pop(self):
-        """ remove """
+        """remove"""
 
         self.f.elts.pop()
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_del_all(self):
-        """ del all """
+        """del all"""
 
         del self.f.elts[:]
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_assign_item(self):
-        """ assign item """
+        """assign item"""
 
         self.f.elts[3] = 99
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_del_item(self):
-        """ del item """
+        """del item"""
 
         del self.f.elts[3]
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_assign_slice(self):
-        """ assign slice """
+        """assign slice"""
 
         self.f.elts[2:4] = [88, 99]
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_del_slice(self):
-        """ del slice """
+        """del slice"""
 
         del self.f.elts[2:5]
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_assign_extended_slice(self):
-        """ assign extended slice """
+        """assign extended slice"""
 
         self.f.elts[2:6:2] = [88, 99]
         # Make sure we successfully recreated the operation.
         self.assertEqual(self.f.elts, listener.clone)
 
     def test_del_extended_slice(self):
-        """ del extended slice """
+        """del extended slice"""
 
         del self.f.elts[2:6:2]
         # Make sure we successfully recreated the operation.
diff --git a/envisage/ui/action/abstract_action_manager_builder.py b/envisage/ui/action/abstract_action_manager_builder.py
index 05789e4bf..98008ee84 100644
--- a/envisage/ui/action/abstract_action_manager_builder.py
+++ b/envisage/ui/action/abstract_action_manager_builder.py
@@ -23,7 +23,7 @@
 
 @provides(IActionManagerBuilder)
 class AbstractActionManagerBuilder(HasTraits):
-    """ Builds menus, menu bars and tool bars from action sets.
+    """Builds menus, menu bars and tool bars from action sets.
 
     This class *must* be subclassed, and the following methods implemented::
 
@@ -47,7 +47,7 @@ class AbstractActionManagerBuilder(HasTraits):
     ###########################################################################
 
     def create_menu_bar_manager(self, root):
-        """ Create a menu bar manager from the builder's action sets. """
+        """Create a menu bar manager from the builder's action sets."""
 
         menu_bar_manager = self._create_menu_bar_manager()
 
@@ -57,7 +57,7 @@ def create_menu_bar_manager(self, root):
 
     # fixme: V3 refactor loooong (and confusing) method!
     def create_tool_bar_managers(self, root):
-        """ Creates all tool bar managers from the builder's action sets. """
+        """Creates all tool bar managers from the builder's action sets."""
 
         ########################################
         # New style (i.e multi) tool bars.
@@ -128,7 +128,7 @@ def create_tool_bar_managers(self, root):
         return tool_bar_managers
 
     def initialize_action_manager(self, action_manager, root):
-        """ Initialize an action manager from the builder's action sets. """
+        """Initialize an action manager from the builder's action sets."""
 
         # Get all of the groups and menus for the specified root (for toolbars
         # there will **only** be groups).
@@ -149,27 +149,27 @@ def initialize_action_manager(self, action_manager, root):
     ###########################################################################
 
     def _create_action(self, action_definition):
-        """ Creates an action implementation from a definition. """
+        """Creates an action implementation from a definition."""
 
         raise NotImplementedError
 
     def _create_group(self, group_definition):
-        """ Creates a group implementation from a definition. """
+        """Creates a group implementation from a definition."""
 
         raise NotImplementedError
 
     def _create_menu_manager(self, menu_manager_definition):
-        """ Creates a menu manager implementation from a definition. """
+        """Creates a menu manager implementation from a definition."""
 
         raise NotImplementedError
 
     def _create_menu_bar_manager(self):
-        """ Creates a menu bar manager implementation. """
+        """Creates a menu bar manager implementation."""
 
         raise NotImplementedError
 
     def _create_tool_bar_manager(self, tool_bar_definition):
-        """ Creates a tool bar manager implementation from a definition. """
+        """Creates a tool bar manager implementation from a definition."""
 
         raise NotImplementedError
 
@@ -181,14 +181,14 @@ def _create_tool_bar_manager(self, tool_bar_definition):
 
     @observe("action_sets")
     def _update_action_sets_on_manager(self, event):
-        """ Static trait change handler. """
+        """Static trait change handler."""
         new = event.new
         self._action_set_manager.action_sets = new
 
     #### Methods ##############################################################
 
     def _add_actions(self, action_manager, actions):
-        """ Add the specified actions to an action manager. """
+        """Add the specified actions to an action manager."""
 
         while len(actions) > 0:
             start = len(actions)
@@ -217,7 +217,7 @@ def _add_actions(self, action_manager, actions):
                 raise ValueError("Could not place %s" % actions)
 
     def _add_action(self, action_manager, action):
-        """ Add an action to an action manager.
+        """Add an action to an action manager.
 
         Return True if the action was added successfully.
 
@@ -253,7 +253,7 @@ def _add_action(self, action_manager, action):
         return True
 
     def _add_groups_and_menus(self, action_manager, groups_and_menus):
-        """ Add the specified groups and menus to an action manager. """
+        """Add the specified groups and menus to an action manager."""
 
         # The reason we put the groups and menus together is that as we iterate
         # over the list trying to add them, we might need to add a group before
@@ -285,7 +285,7 @@ def _add_groups_and_menus(self, action_manager, groups_and_menus):
                 raise ValueError("Could not place %s" % groups_and_menus)
 
     def _add_group(self, action_manager, group):
-        """ Add a group to an action manager.
+        """Add a group to an action manager.
 
         Return True if the group was added successfully.
 
@@ -328,7 +328,7 @@ def _add_group(self, action_manager, group):
         return True
 
     def _add_menu(self, menu_manager, menu):
-        """ Add a menu manager to a errr, menu manager.
+        """Add a menu manager to a errr, menu manager.
 
         Return True if the menu was added successfully.
 
@@ -371,7 +371,7 @@ def _add_menu(self, menu_manager, menu):
         return True
 
     def _find_group(self, action_manager, id):
-        """ Find the group with the specified ID. """
+        """Find the group with the specified ID."""
 
         if len(id) > 0:
             group = action_manager.find_group(id)
@@ -382,7 +382,7 @@ def _find_group(self, action_manager, id):
         return group
 
     def _find_action_manager(self, action_manager, path):
-        """ Return the action manager at the specified path.
+        """Return the action manager at the specified path.
 
         Returns None if the action manager cannot be found.
 
@@ -398,7 +398,7 @@ def _find_action_manager(self, action_manager, path):
         return action_manager
 
     def _make_submenus(self, menu_manager, path):
-        """ Retutn the menu manager identified by the path.
+        """Retutn the menu manager identified by the path.
 
         Make any intermediate menu-managers that are missing.
 
diff --git a/envisage/ui/action/action.py b/envisage/ui/action/action.py
index 3fa2d9131..ae358e747 100644
--- a/envisage/ui/action/action.py
+++ b/envisage/ui/action/action.py
@@ -18,7 +18,7 @@
 
 
 class Action(Location):
-    """ The *definition* of an action in a tool bar or menu. """
+    """The *definition* of an action in a tool bar or menu."""
 
     #### Action implementation ################################################
 
@@ -33,7 +33,7 @@ class Action(Location):
     ###########################################################################
 
     def __str__(self):
-        """ Return the 'informal' string representation of the object. """
+        """Return the 'informal' string representation of the object."""
 
         return "Action(%s)" % self.name
 
diff --git a/envisage/ui/action/action_set.py b/envisage/ui/action/action_set.py
index d170669b1..cf59b0acc 100644
--- a/envisage/ui/action/action_set.py
+++ b/envisage/ui/action/action_set.py
@@ -14,16 +14,15 @@
 import logging
 
 # Enthought library imports.
-from traits.api import Bool, Dict, HasTraits, List, Str, provides
+from traits.api import Bool, Dict, HasTraits, List, provides, Str
 from traits.util.camel_case import camel_case_to_words
 
 # Local imports.
 from .action import Action
 from .group import Group
+from .i_action_set import IActionSet
 from .menu import Menu
 from .tool_bar import ToolBar
-from .i_action_set import IActionSet
-
 
 # Logging.
 logger = logging.getLogger(__name__)
@@ -31,7 +30,7 @@
 
 @provides(IActionSet)
 class ActionSet(HasTraits):
-    """ An action set is a collection of menus, groups, and actions. """
+    """An action set is a collection of menus, groups, and actions."""
 
     # The action set's globally unique identifier.
     id = Str
@@ -97,7 +96,7 @@ class ActionSet(HasTraits):
     #### Trait initializers ###################################################
 
     def _id_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         id = "%s.%s" % (type(self).__module__, type(self).__name__)
         logger.warning("action set %s has no Id - using <%s>" % (self, id))
@@ -105,7 +104,7 @@ def _id_default(self):
         return id
 
     def _name_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         name = camel_case_to_words(type(self).__name__)
         logger.warning("action set %s has no name - using <%s>" % (self, name))
diff --git a/envisage/ui/action/action_set_manager.py b/envisage/ui/action/action_set_manager.py
index a32748ee2..1b994d3cc 100644
--- a/envisage/ui/action/action_set_manager.py
+++ b/envisage/ui/action/action_set_manager.py
@@ -18,7 +18,7 @@
 
 
 class ActionSetManager(HasTraits):
-    """ Manages a collection of action sets. """
+    """Manages a collection of action sets."""
 
     #### 'ActionSetManager' interface #########################################
 
@@ -30,22 +30,22 @@ class ActionSetManager(HasTraits):
     ###########################################################################
 
     def get_actions(self, root):
-        """ Return all action definitions for a root. """
+        """Return all action definitions for a root."""
 
         return self._get_items(self.action_sets, "actions", root)
 
     def get_groups(self, root):
-        """ Return all group definitions for a root. """
+        """Return all group definitions for a root."""
 
         return self._get_items(self.action_sets, "groups", root)
 
     def get_menus(self, root):
-        """ Return all menu definitions for a root. """
+        """Return all menu definitions for a root."""
 
         return self._get_items(self.action_sets, "menus", root)
 
     def get_tool_bars(self, root):
-        """ Return all tool bar definitions for a root. """
+        """Return all tool bar definitions for a root."""
 
         return self._get_items(self.action_sets, "tool_bars", root)
 
@@ -54,7 +54,7 @@ def get_tool_bars(self, root):
     ###########################################################################
 
     def _get_items(self, action_sets, attribute_name, root):
-        """ Return all actions, groups or menus for a particular root.
+        """Return all actions, groups or menus for a particular root.
 
         e.g. To get all of the groups::
 
@@ -81,7 +81,7 @@ def _get_items(self, action_sets, attribute_name, root):
         return items
 
     def _get_root(self, path, aliases):
-        """ Return the effective root for a path.
+        """Return the effective root for a path.
 
         If the first component of the path matches an alias, then we return
         the value of the alias.
diff --git a/envisage/ui/action/api.py b/envisage/ui/action/api.py
index 36fb52a4a..7b462d3ce 100644
--- a/envisage/ui/action/api.py
+++ b/envisage/ui/action/api.py
@@ -7,12 +7,11 @@
 # is also available online at http://www.enthought.com/licenses/BSD.txt
 #
 # Thanks for using Enthought open source!
-from .i_action_set import IActionSet
-from .i_action_manager_builder import IActionManagerBuilder
-
 from .abstract_action_manager_builder import AbstractActionManagerBuilder
 from .action import Action
 from .action_set import ActionSet
 from .group import Group
+from .i_action_manager_builder import IActionManagerBuilder
+from .i_action_set import IActionSet
 from .menu import Menu
 from .tool_bar import ToolBar
diff --git a/envisage/ui/action/group.py b/envisage/ui/action/group.py
index 9c22849bf..ba4cf1d61 100644
--- a/envisage/ui/action/group.py
+++ b/envisage/ui/action/group.py
@@ -18,7 +18,7 @@
 
 
 class Group(Location):
-    """ The *definition* of a group in a tool bar or menu. """
+    """The *definition* of a group in a tool bar or menu."""
 
     # The group's unique identifier (unique within the tool bar, menu bar or
     # menu that the group is to be added to).
@@ -36,7 +36,7 @@ class Group(Location):
     ###########################################################################
 
     def __str__(self):
-        """ Return the 'informal' string representation of the object. """
+        """Return the 'informal' string representation of the object."""
 
         return "Group(%s)" % self.id
 
diff --git a/envisage/ui/action/i_action_manager_builder.py b/envisage/ui/action/i_action_manager_builder.py
index ee1cb5a0e..488c90cd9 100644
--- a/envisage/ui/action/i_action_manager_builder.py
+++ b/envisage/ui/action/i_action_manager_builder.py
@@ -18,7 +18,7 @@
 
 
 class IActionManagerBuilder(Interface):
-    """ The interface for action manager builders.
+    """The interface for action manager builders.
 
     An action manager builder populates action managers (i.e. menus, menu bars
     and tool bars) from the menus, groups and actions defined in its action
@@ -30,6 +30,4 @@ class IActionManagerBuilder(Interface):
     action_sets = List(ActionSet)
 
     def initialize_action_manager(self, action_manager, root):
-        """ Initialize an action manager from the builder's action sets.
-
-        """
+        """Initialize an action manager from the builder's action sets."""
diff --git a/envisage/ui/action/i_action_set.py b/envisage/ui/action/i_action_set.py
index 77ecb6e2d..7aabe94da 100644
--- a/envisage/ui/action/i_action_set.py
+++ b/envisage/ui/action/i_action_set.py
@@ -21,7 +21,7 @@
 
 
 class IActionSet(Interface):
-    """ The action set interface.
+    """The action set interface.
 
     An action set is a collection of menus, groups, and actions.
 
diff --git a/envisage/ui/action/location.py b/envisage/ui/action/location.py
index 5a67e2ca9..03772fc45 100644
--- a/envisage/ui/action/location.py
+++ b/envisage/ui/action/location.py
@@ -15,9 +15,7 @@
 
 
 class Location(HasTraits):
-    """ The location of a group, menu, or action, within an action hierarchy.
-
-    """
+    """The location of a group, menu, or action, within an action hierarchy."""
 
     # A forward-slash-separated path through the action hierarchy to the menu
     # to add the action, group or menu to.
diff --git a/envisage/ui/action/menu.py b/envisage/ui/action/menu.py
index 3f5f897fb..9cedd9273 100644
--- a/envisage/ui/action/menu.py
+++ b/envisage/ui/action/menu.py
@@ -18,7 +18,7 @@
 
 
 class CGroup(Instance):
-    """ A trait type for a 'Group' or anything that can be cast to a 'Group'.
+    """A trait type for a 'Group' or anything that can be cast to a 'Group'.
 
     Currently, the only cast allowed is from string -> Group using the
     string as the group's ID.
@@ -30,7 +30,7 @@ class CGroup(Instance):
     ###########################################################################
 
     def __init__(self, **kw):
-        """ Constructor. """
+        """Constructor."""
 
         super().__init__(klass=Group, **kw)
 
@@ -39,7 +39,7 @@ def __init__(self, **kw):
     ###########################################################################
 
     def validate(self, object, name, value):
-        """ Validate a value. """
+        """Validate a value."""
 
         if isinstance(value, str):
             value = Group(id=value)
@@ -48,7 +48,7 @@ def validate(self, object, name, value):
 
 
 class Menu(Location):
-    """ The *definition* of a menu in a menu bar or menu. """
+    """The *definition* of a menu in a menu bar or menu."""
 
     # The menu's unique identifier (unique within the group that the menu is to
     # be added to).
@@ -69,7 +69,7 @@ class Menu(Location):
     ###########################################################################
 
     def __str__(self):
-        """ Return the 'informal' string representation of the object. """
+        """Return the 'informal' string representation of the object."""
 
         return "Menu(%s)" % self.name
 
@@ -80,6 +80,6 @@ def __str__(self):
     ###########################################################################
 
     def _id_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return self.name.strip("&")
diff --git a/envisage/ui/action/tests/dummy_action_manager_builder.py b/envisage/ui/action/tests/dummy_action_manager_builder.py
index c8e6ae26f..510b67454 100644
--- a/envisage/ui/action/tests/dummy_action_manager_builder.py
+++ b/envisage/ui/action/tests/dummy_action_manager_builder.py
@@ -9,14 +9,14 @@
 # Thanks for using Enthought open source!
 """ A menu builder that doesn't build real actions! """
 
+from pyface.action.api import Action, Group, MenuBarManager, MenuManager
+
 # Enthought library imports.
 from envisage.ui.action.api import AbstractActionManagerBuilder
-from pyface.action.api import Action, Group, MenuManager
-from pyface.action.api import MenuBarManager
 
 
 class DummyActionManagerBuilder(AbstractActionManagerBuilder):
-    """ An action manager builder that doesn't build real actions!
+    """An action manager builder that doesn't build real actions!
 
     This makes it very easy to test!
 
@@ -27,7 +27,7 @@ class DummyActionManagerBuilder(AbstractActionManagerBuilder):
     ###########################################################################
 
     def create_menu_bar_manager(self, root):
-        """ Create a menu bar manager from the builder's action sets. """
+        """Create a menu bar manager from the builder's action sets."""
 
         menu_bar_manager = MenuBarManager(id="MenuBar")
 
@@ -40,17 +40,17 @@ def create_menu_bar_manager(self, root):
     ###########################################################################
 
     def _create_action(self, action_definition):
-        """ Create an action implementation from a definition. """
+        """Create an action implementation from a definition."""
 
         return Action(name=action_definition.class_name)
 
     def _create_group(self, group_definition):
-        """ Create a group implementation from a definition. """
+        """Create a group implementation from a definition."""
 
         return Group(id=group_definition.id)
 
     def _create_menu_manager(self, menu_definition):
-        """ Create a menu manager implementation from a definition. """
+        """Create a menu manager implementation from a definition."""
 
         menu_manager = MenuManager(id=menu_definition.id)
         for group_definition in menu_definition.groups:
diff --git a/envisage/ui/action/tests/test_action_manager_builder.py b/envisage/ui/action/tests/test_action_manager_builder.py
index eacf15b86..f71c5d099 100644
--- a/envisage/ui/action/tests/test_action_manager_builder.py
+++ b/envisage/ui/action/tests/test_action_manager_builder.py
@@ -20,10 +20,10 @@
 
 
 class ActionManagerBuilderTestCase(unittest.TestCase):
-    """ Tests for the action manager builder. """
+    """Tests for the action manager builder."""
 
     def test_action_with_nonexistent_group(self):
-        """ action with non-existent group """
+        """action with non-existent group"""
 
         action_sets = [
             ActionSet(
@@ -43,7 +43,7 @@ def test_action_with_nonexistent_group(self):
             builder.create_menu_bar_manager("MenuBar")
 
     def test_action_with_nonexistent_sibling(self):
-        """ action with non-existent sibling """
+        """action with non-existent sibling"""
 
         action_sets = [
             ActionSet(
@@ -65,7 +65,7 @@ def test_action_with_nonexistent_sibling(self):
             builder.create_menu_bar_manager("MenuBar")
 
     def test_group_with_nonexistent_sibling(self):
-        """ group with non-existent sibling """
+        """group with non-existent sibling"""
 
         action_sets = [
             ActionSet(
@@ -83,7 +83,7 @@ def test_group_with_nonexistent_sibling(self):
             builder.create_menu_bar_manager("MenuBar")
 
     def test_menu_with_nonexistent_sibling(self):
-        """ menu with non-existent sibling """
+        """menu with non-existent sibling"""
 
         action_sets = [
             ActionSet(
@@ -99,7 +99,7 @@ def test_menu_with_nonexistent_sibling(self):
             builder.create_menu_bar_manager("MenuBar")
 
     def test_action_with_path_component_that_is_not_a_menu(self):
-        """ action with path component that is not a menu """
+        """action with path component that is not a menu"""
 
         action_sets = [
             ActionSet(
@@ -118,7 +118,7 @@ def test_action_with_path_component_that_is_not_a_menu(self):
             builder.create_menu_bar_manager("MenuBar")
 
     def test_single_top_level_menu_with_no_group(self):
-        """ single top level menu with no group """
+        """single top level menu with no group"""
 
         action_sets = [ActionSet(menus=[Menu(name="&File", path="MenuBar")])]
 
@@ -137,7 +137,7 @@ def test_single_top_level_menu_with_no_group(self):
         self.assertEqual(["File"], ids)
 
     def test_single_top_level_group(self):
-        """ single top level group """
+        """single top level group"""
 
         action_sets = [
             ActionSet(groups=[Group(id="FileMenuGroup", path="MenuBar")])
@@ -156,7 +156,7 @@ def test_single_top_level_group(self):
         self.assertEqual(["FileMenuGroup", "additions"], ids)
 
     def test_top_level_menus_with_no_groups(self):
-        """ top level menus with_no groups """
+        """top level menus with_no groups"""
 
         action_sets = [
             ActionSet(
@@ -184,7 +184,7 @@ def test_top_level_menus_with_no_groups(self):
         self.assertEqual(["File", "Edit", "Tools", "Help"], ids)
 
     def test_top_level_menus_no_groups_before_and_after(self):
-        """ top level menus no groups, before and after """
+        """top level menus no groups, before and after"""
 
         action_sets = [
             ActionSet(
@@ -212,7 +212,7 @@ def test_top_level_menus_no_groups_before_and_after(self):
         self.assertEqual(["File", "Edit", "Tools", "Help"], ids)
 
     def test_top_level_menu_non_existent_group(self):
-        """ top level menu non-existent group """
+        """top level menu non-existent group"""
 
         action_sets = [
             ActionSet(
@@ -230,7 +230,7 @@ def test_top_level_menu_non_existent_group(self):
             builder.create_menu_bar_manager("MenuBar")
 
     def test_top_level_menu_group(self):
-        """ top level menu group """
+        """top level menu group"""
 
         action_sets = [
             ActionSet(
@@ -258,7 +258,7 @@ def test_top_level_menu_group(self):
         self.assertEqual("File", group.items[0].id)
 
     def test_sub_menus_no_groups(self):
-        """ sub-menus no groups """
+        """sub-menus no groups"""
 
         # We split the contributions into different action sets just because
         # that is how it might end up in an actual application... not because
@@ -289,7 +289,7 @@ def test_sub_menus_no_groups(self):
         self.assertEqual("New", additions.items[0].id)
 
     def test_actions_no_groups(self):
-        """ actions no groups """
+        """actions no groups"""
 
         # We split the contributions into different action sets just because
         # that is how it might end up in an actual application... not because
@@ -332,7 +332,7 @@ def test_actions_no_groups(self):
         self.assertEqual("About", additions.items[0].id)
 
     def test_actions_make_submenus(self):
-        """ actions make submenus """
+        """actions make submenus"""
 
         action_sets = [
             ActionSet(
@@ -372,7 +372,7 @@ def test_actions_make_submenus(self):
         self.assertEqual("File", additions.items[1].id)
 
     def test_actions_make_submenus_before_and_after(self):
-        """ actions make submenus before and after """
+        """actions make submenus before and after"""
 
         action_sets = [
             ActionSet(
@@ -421,7 +421,7 @@ def test_actions_make_submenus_before_and_after(self):
         self.assertEqual(["Project", "Folder", "File"], ids)
 
     def test_explicit_groups(self):
-        """ explicit groups """
+        """explicit groups"""
 
         action_sets = [
             ActionSet(
@@ -498,7 +498,7 @@ def test_explicit_groups(self):
         self.assertEqual("Exit", group.items[0].id)
 
     def test_actions_and_menus_in_groups(self):
-        """ actions and menus in groups """
+        """actions and menus in groups"""
 
         action_sets = [
             ActionSet(
@@ -573,7 +573,7 @@ def test_actions_and_menus_in_groups(self):
         self.assertEqual("Exit", group.items[0].id)
 
     def test_duplicate_menu(self):
-        """ duplicate menu """
+        """duplicate menu"""
 
         action_sets = [
             ActionSet(
@@ -627,7 +627,7 @@ def test_duplicate_menu(self):
         )
 
     def test_duplicate_group(self):
-        """ duplicate group """
+        """duplicate group"""
 
         action_sets = [
             ActionSet(
@@ -639,7 +639,6 @@ def test_duplicate_group(self):
                             Group(id="NewGroup", path="MenuBar/File"),
                             Group(id="ExitGroup", path="MenuBar/File"),
                         ],
-
                     ),
                 ],
             ),
diff --git a/envisage/ui/action/tool_bar.py b/envisage/ui/action/tool_bar.py
index 4786eba45..b4ac5aac8 100644
--- a/envisage/ui/action/tool_bar.py
+++ b/envisage/ui/action/tool_bar.py
@@ -19,7 +19,7 @@
 
 # fixme: Remove duplication (in menu.py too!)
 class CGroup(Instance):
-    """ A trait type for a 'Group' or anything that can be cast to a 'Group'.
+    """A trait type for a 'Group' or anything that can be cast to a 'Group'.
 
     Currently, the only cast allowed is from string -> Group using the
     string as the group's ID.
@@ -31,7 +31,7 @@ class CGroup(Instance):
     ###########################################################################
 
     def __init__(self, **kw):
-        """ Constructor. """
+        """Constructor."""
 
         super().__init__(klass=Group, **kw)
 
@@ -40,7 +40,7 @@ def __init__(self, **kw):
     ###########################################################################
 
     def validate(self, object, name, value):
-        """ Validate a value. """
+        """Validate a value."""
 
         if isinstance(value, str):
             value = Group(id=value)
@@ -49,7 +49,7 @@ def validate(self, object, name, value):
 
 
 class ToolBar(Location):
-    """ The *definition* of a menu in a menu bar or menu. """
+    """The *definition* of a menu in a menu bar or menu."""
 
     # The tool bars's unique identifier (unique within the multi-toolbar
     # that the tool bar is to be added to).
@@ -70,7 +70,7 @@ class ToolBar(Location):
     ###########################################################################
 
     def __str__(self):
-        """ Return the 'informal' string representation of the object. """
+        """Return the 'informal' string representation of the object."""
 
         return "ToolBar(%s)" % self.name
 
@@ -81,7 +81,7 @@ def __str__(self):
     ###########################################################################
 
     def _path_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return "ToolBar"
 
@@ -90,6 +90,6 @@ def _path_default(self):
     ###########################################################################
 
     def _id_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return self.name
diff --git a/envisage/ui/gui_application.py b/envisage/ui/gui_application.py
index ca9916a46..4af485a39 100644
--- a/envisage/ui/gui_application.py
+++ b/envisage/ui/gui_application.py
@@ -22,11 +22,12 @@
 """
 
 from traits.api import Event, Supports
+
 from envisage.api import Application
 
 
 class GUIApplication(Application):
-    """ The entry point for an Envisage GUI application.
+    """The entry point for an Envisage GUI application.
 
     This class handles the life-cycle of a Pyface GUI.  Plugins can
     display windows via mechinisms such as edit_traits().
@@ -57,7 +58,7 @@ class GUIApplication(Application):
     ###########################################################################
 
     def run(self):
-        """ Run the application.
+        """Run the application.
 
         Returns
         -------
diff --git a/envisage/ui/tasks/action/exit_action.py b/envisage/ui/tasks/action/exit_action.py
index 4d35e16c5..af9af68c0 100644
--- a/envisage/ui/tasks/action/exit_action.py
+++ b/envisage/ui/tasks/action/exit_action.py
@@ -12,8 +12,7 @@
 
 
 class ExitAction(Action):
-    """ An action that exits the application.
-    """
+    """An action that exits the application."""
 
     #### 'Action' interface ###################################################
 
diff --git a/envisage/ui/tasks/action/preferences_action.py b/envisage/ui/tasks/action/preferences_action.py
index b9771bc46..2955af976 100644
--- a/envisage/ui/tasks/action/preferences_action.py
+++ b/envisage/ui/tasks/action/preferences_action.py
@@ -12,8 +12,7 @@
 
 
 class PreferencesAction(Action):
-    """ An action that displays the preferences dialog.
-    """
+    """An action that displays the preferences dialog."""
 
     #### 'Action' interface ###################################################
 
@@ -42,8 +41,7 @@ def perform(self, event):
 
 
 class PreferencesGroup(Group):
-    """ A group that contains the preferences action.
-    """
+    """A group that contains the preferences action."""
 
     #### 'Action' interface ###################################################
 
diff --git a/envisage/ui/tasks/action/task_window_launch_group.py b/envisage/ui/tasks/action/task_window_launch_group.py
index b178d84b6..f78652633 100644
--- a/envisage/ui/tasks/action/task_window_launch_group.py
+++ b/envisage/ui/tasks/action/task_window_launch_group.py
@@ -10,14 +10,13 @@
 
 # Enthought library imports.
 from pyface.action.api import ActionItem, Group
-from pyface.tasks.api import TaskWindowLayout
 from pyface.tasks.action.api import TaskAction
+from pyface.tasks.api import TaskWindowLayout
 from traits.api import List, observe, Str
 
 
 class TaskWindowLaunchAction(TaskAction):
-    """ An Action that creates a task window with a single task.
-    """
+    """An Action that creates a task window with a single task."""
 
     #### 'TaskWindowLaunchAction' interface ###################################
 
@@ -40,8 +39,7 @@ def perform(self, event):
 
     @observe("task")
     def _update_name(self, event):
-        """ Name the action (unless a name has already been assigned).
-        """
+        """Name the action (unless a name has already been assigned)."""
         task = event.new
         if task and not self.name:
             name = ""
@@ -53,8 +51,7 @@ def _update_name(self, event):
 
 
 class TaskWindowLaunchGroup(Group):
-    """ A Group for creating task windows with a single task.
-    """
+    """A Group for creating task windows with a single task."""
 
     #### 'Group' interface ####################################################
 
diff --git a/envisage/ui/tasks/action/task_window_toggle_group.py b/envisage/ui/tasks/action/task_window_toggle_group.py
index 6e499a9fd..9978ae002 100644
--- a/envisage/ui/tasks/action/task_window_toggle_group.py
+++ b/envisage/ui/tasks/action/task_window_toggle_group.py
@@ -9,12 +9,11 @@
 # Thanks for using Enthought open source!
 # Enthought library imports.
 from pyface.action.api import Action, ActionItem, Group
-from traits.api import Any, Instance, List, Property, Str, on_trait_change
+from traits.api import Any, Instance, List, on_trait_change, Property, Str
 
 
 class TaskWindowToggleAction(Action):
-    """ An action for activating an application window.
-    """
+    """An action for activating an application window."""
 
     #### 'Action' interface ###################################################
 
@@ -53,7 +52,8 @@ def _window_deactivated(self):
 
 
 class TaskWindowToggleGroup(Group):
-    """ A Group for toggling the activation state of an application's windows.
+    """
+    A Group for toggling the activation state of an application's windows.
     """
 
     #### 'Group' interface ####################################################
@@ -76,8 +76,7 @@ class TaskWindowToggleGroup(Group):
     ###########################################################################
 
     def destroy(self):
-        """ Called when the group is no longer required.
-        """
+        """Called when the group is no longer required."""
         super().destroy()
         if self.application:
             self.application.on_trait_change(
diff --git a/envisage/ui/tasks/preferences_category.py b/envisage/ui/tasks/preferences_category.py
index 35a6262df..7b1531550 100644
--- a/envisage/ui/tasks/preferences_category.py
+++ b/envisage/ui/tasks/preferences_category.py
@@ -12,8 +12,7 @@
 
 
 class PreferencesCategory(HasTraits):
-    """ The description for a container of PreferencesPanes.
-    """
+    """The description for a container of PreferencesPanes."""
 
     # The globally unique identifier for the category.
     id = Str
@@ -32,6 +31,5 @@ class PreferencesCategory(HasTraits):
     ###########################################################################
 
     def _name_default(self):
-        """ By default, use the ID for the name.
-        """
+        """By default, use the ID for the name."""
         return self.id
diff --git a/envisage/ui/tasks/preferences_dialog.py b/envisage/ui/tasks/preferences_dialog.py
index 9095cae34..96c0e9979 100644
--- a/envisage/ui/tasks/preferences_dialog.py
+++ b/envisage/ui/tasks/preferences_dialog.py
@@ -8,9 +8,9 @@
 #
 # Thanks for using Enthought open source!
 # Enthought library imports.
-from traits.api import Bool, HasTraits, Instance, List, Str, on_trait_change
-from traitsui.api import Item, Handler, ListEditor, View
 from pyface.tasks.topological_sort import before_after_sort
+from traits.api import Bool, HasTraits, Instance, List, on_trait_change, Str
+from traitsui.api import Handler, Item, ListEditor, View
 
 # Local imports.
 from .preferences_category import PreferencesCategory
@@ -18,8 +18,7 @@
 
 
 class PreferencesTab(HasTraits):
-    """ An object used internally by PreferencesDialog.
-    """
+    """An object used internally by PreferencesDialog."""
 
     name = Str
     panes = List(PreferencesPane)
@@ -36,8 +35,7 @@ class PreferencesTab(HasTraits):
 
 
 class PreferencesDialog(Handler):
-    """ A dialog for editing preferences.
-    """
+    """A dialog for editing preferences."""
 
     #### 'PreferencesDialog' interface ########################################
 
@@ -63,7 +61,8 @@ class PreferencesDialog(Handler):
     ###########################################################################
 
     def select_pane(self, pane_id):
-        """ Find and activate the notebook tab that contains the given pane id.
+        """
+        Find and activate the notebook tab that contains the given pane id.
         """
         for tab in self._tabs:
             for pane in tab.panes:
@@ -76,14 +75,13 @@ def select_pane(self, pane_id):
     ###########################################################################
 
     def trait_context(self):
-        """ Returns the default context to use for editing or configuring
-            traits.
+        """Returns the default context to use for editing or configuring
+        traits.
         """
         return {"object": self, "handler": self}
 
     def traits_view(self):
-        """ Build the dynamic dialog view.
-        """
+        """Build the dynamic dialog view."""
         buttons = ["OK", "Cancel"]
         if self.show_apply:
             buttons = ["Apply"] + buttons
@@ -114,14 +112,14 @@ def traits_view(self):
     ###########################################################################
 
     def apply(self, info=None):
-        """ Handles the Apply button being clicked.
-        """
+        """Handles the Apply button being clicked."""
         for tab in self._tabs:
             for pane in tab.panes:
                 pane.apply()
 
     def close(self, info, is_ok):
-        """ Handles the user attempting to close a dialog-based user interface.
+        """
+        Handles the user attempting to close a dialog-based user interface.
         """
         if is_ok:
             self.apply()
diff --git a/envisage/ui/tasks/preferences_pane.py b/envisage/ui/tasks/preferences_pane.py
index e7aa55dc7..bfa89aa84 100644
--- a/envisage/ui/tasks/preferences_pane.py
+++ b/envisage/ui/tasks/preferences_pane.py
@@ -14,8 +14,7 @@
 
 
 class PreferencesPane(Controller):
-    """ A panel for configuring application preferences.
-    """
+    """A panel for configuring application preferences."""
 
     #### 'Controller' interface ###############################################
 
@@ -55,8 +54,8 @@ class PreferencesPane(Controller):
     ###########################################################################
 
     def trait_context(self):
-        """ Re-implemented to use a copy of the model that is not connected to
-            the preferences node.
+        """Re-implemented to use a copy of the model that is not connected to
+        the preferences node.
         """
         if self.model is None:
             if self.model_factory is not None:
@@ -74,15 +73,15 @@ def trait_context(self):
     ###########################################################################
 
     def apply(self, info=None):
-        """ Handles the Apply button being clicked.
-        """
+        """Handles the Apply button being clicked."""
         trait_names = list(
             filter(self._model._is_preference_trait, self._model.trait_names())
         )
         self.model.copy_traits(self._model, trait_names)
 
     def close(self, info, is_ok):
-        """ Handles the user attempting to close a dialog-based user interface.
+        """
+        Handles the user attempting to close a dialog-based user interface.
         """
         if is_ok:
             self.apply()
diff --git a/envisage/ui/tasks/task_extension.py b/envisage/ui/tasks/task_extension.py
index 17d5442f7..6cf4310d6 100644
--- a/envisage/ui/tasks/task_extension.py
+++ b/envisage/ui/tasks/task_extension.py
@@ -9,12 +9,11 @@
 # Thanks for using Enthought open source!
 # Enthought library imports.
 from pyface.tasks.action.api import SchemaAddition
-from traits.api import HasStrictTraits, Callable, List, Str
+from traits.api import Callable, HasStrictTraits, List, Str
 
 
 class TaskExtension(HasStrictTraits):
-    """ A bundle of items for extending a Task.
-    """
+    """A bundle of items for extending a Task."""
 
     #: The ID of the task to extend. If the ID is omitted, the extension
     #: applies to all tasks.
diff --git a/envisage/ui/tasks/task_factory.py b/envisage/ui/tasks/task_factory.py
index 3d9c13604..42b5a666f 100644
--- a/envisage/ui/tasks/task_factory.py
+++ b/envisage/ui/tasks/task_factory.py
@@ -12,8 +12,7 @@
 
 
 class TaskFactory(HasTraits):
-    """ A factory for creating a Task with some additional metadata.
-    """
+    """A factory for creating a Task with some additional metadata."""
 
     #: The task factory's unique identifier. This ID is assigned to all tasks
     #: created by the factory.
@@ -30,15 +29,14 @@ class TaskFactory(HasTraits):
     factory = Callable
 
     def create(self, **traits):
-        """ Creates the Task.
+        """Creates the Task.
 
         The default implementation simply calls the 'factory' attribute.
         """
         return self.factory(**traits)
 
     def create_with_extensions(self, extensions, **traits):
-        """ Creates the Task using the specified TaskExtensions.
-        """
+        """Creates the Task using the specified TaskExtensions."""
         task = self.create(**traits)
         for extension in extensions:
             task.extra_actions.extend(extension.actions)
diff --git a/envisage/ui/tasks/task_window.py b/envisage/ui/tasks/task_window.py
index faf18f41c..b132d57b7 100644
--- a/envisage/ui/tasks/task_window.py
+++ b/envisage/ui/tasks/task_window.py
@@ -15,8 +15,7 @@
 
 
 class TaskWindow(PyfaceTaskWindow):
-    """ A TaskWindow for use with the Envisage Tasks plugin.
-    """
+    """A TaskWindow for use with the Envisage Tasks plugin."""
 
     #: The application that created and is managing this window.
     application = Instance("envisage.ui.tasks.api.TasksApplication")
@@ -34,8 +33,8 @@ class TaskWindow(PyfaceTaskWindow):
     ###########################################################################
 
     def _get_title(self):
-        """ If the application has a name, add it to the title. Otherwise,
-            behave like the base class.
+        """If the application has a name, add it to the title. Otherwise,
+        behave like the base class.
         """
         if self._title or self.active_task is None:
             return self._title
@@ -47,8 +46,7 @@ def _get_title(self):
         return title
 
     def _get_icon(self):
-        """If we have an icon return it, else delegate to the application.
-        """
+        """If we have an icon return it, else delegate to the application."""
         if self._icon is not None:
             return self._icon
         elif self.application is not None:
@@ -57,6 +55,5 @@ def _get_icon(self):
             return None
 
     def _set_icon(self, icon):
-        """Explicitly set the icon to use.  None is allowed.
-        """
+        """Explicitly set the icon to use.  None is allowed."""
         self._icon = icon
diff --git a/envisage/ui/tasks/task_window_event.py b/envisage/ui/tasks/task_window_event.py
index dd500558b..90603c7b7 100644
--- a/envisage/ui/tasks/task_window_event.py
+++ b/envisage/ui/tasks/task_window_event.py
@@ -15,15 +15,13 @@
 
 
 class TaskWindowEvent(HasTraits):
-    """ A task window lifecycle event.
-    """
+    """A task window lifecycle event."""
 
     #: The window that the event occurred on.
     window = Instance(TaskWindow)
 
 
 class VetoableTaskWindowEvent(TaskWindowEvent, Vetoable):
-    """ A vetoable task window lifecycle event.
-    """
+    """A vetoable task window lifecycle event."""
 
     pass
diff --git a/envisage/ui/tasks/tasks_application.py b/envisage/ui/tasks/tasks_application.py
index cb9d6ca99..40eef55df 100644
--- a/envisage/ui/tasks/tasks_application.py
+++ b/envisage/ui/tasks/tasks_application.py
@@ -9,11 +9,9 @@
 # Thanks for using Enthought open source!
 # Standard library imports.
 import logging
-import pickle
 import os.path
+import pickle
 
-# Enthought library imports.
-from envisage.api import Application, ExtensionPoint
 from traits.api import (
     Bool,
     Callable,
@@ -28,6 +26,8 @@
 )
 from traits.etsconfig.api import ETSConfig
 
+# Enthought library imports.
+from envisage.api import Application, ExtensionPoint
 
 # Logging.
 logger = logging.getLogger(__name__)
@@ -157,7 +157,7 @@ class TasksApplication(Application):
     ###########################################################################
 
     def run(self):
-        """ Run the application.
+        """Run the application.
 
         Returns
         -------
@@ -186,7 +186,7 @@ def run(self):
     ###########################################################################
 
     def create_task(self, id):
-        """ Creates the Task with the specified ID.
+        """Creates the Task with the specified ID.
 
         Returns
         -------
@@ -234,9 +234,10 @@ def create_window(self, layout=None, restore=True, **traits):
             The new TaskWindow.
 
         """
-        from .task_window_event import TaskWindowEvent
         from pyface.tasks.task_window_layout import TaskWindowLayout
 
+        from .task_window_event import TaskWindowEvent
+
         window = self.window_factory(application=self, **traits)
 
         # Listen for the window events.
@@ -318,8 +319,8 @@ def exit(self, force=False):
     ###########################################################################
 
     def _create_windows(self):
-        """ Called at startup to create TaskWindows from the default or saved
-            application layout.
+        """Called at startup to create TaskWindows from the default or saved
+        application layout.
         """
         # Build a list of TaskWindowLayouts.
         self._load_state()
@@ -355,23 +356,21 @@ def _create_windows(self):
             window.open()
 
     def _get_task_factory(self, id):
-        """ Returns the TaskFactory with the specified ID, or None.
-        """
+        """Returns the TaskFactory with the specified ID, or None."""
         for factory in self.task_factories:
             if factory.id == id:
                 return factory
         return None
 
     def _prepare_exit(self):
-        """ Called immediately before the extant windows are destroyed and the
-            GUI event loop is terminated.
+        """Called immediately before the extant windows are destroyed and the
+        GUI event loop is terminated.
         """
         self.application_exiting = self
         self._save_state()
 
     def _load_state(self):
-        """ Loads saved application state, if possible.
-        """
+        """Loads saved application state, if possible."""
         state = TasksApplicationState()
         filename = os.path.join(self.state_location, self.state_filename)
         if os.path.exists(filename):
@@ -400,8 +399,7 @@ def _load_state(self):
         self._state = state
 
     def _restore_layout_from_state(self, layout):
-        """ Restores an equivalent layout from saved application state.
-        """
+        """Restores an equivalent layout from saved application state."""
         # First, see if a window layout matches exactly.
         match = self._state.get_equivalent_window_layout(layout)
         if match:
@@ -423,8 +421,7 @@ def _restore_layout_from_state(self, layout):
         return layout
 
     def _save_state(self):
-        """ Saves the application state.
-        """
+        """Saves the application state."""
         # Grab the current window layouts.
         window_layouts = [w.get_window_layout() for w in self.windows]
         self._state.previous_window_layouts = window_layouts
@@ -442,8 +439,7 @@ def _save_state(self):
             logger.debug("Application state successfully saved")
 
     def _initialize_application_home(self):
-        """ Initialize the application directories.
-        """
+        """Initialize the application directories."""
         # Extend the base class method to ensure the state directory exists.
         super()._initialize_application_home()
 
@@ -535,8 +531,8 @@ def _on_window_closed(self, window, trait_name, event):
 
 
 class TasksApplicationState(HasStrictTraits):
-    """ A class used internally by TasksApplication for saving and restoring
-        application state.
+    """A class used internally by TasksApplication for saving and restoring
+    application state.
     """
 
     # TaskWindowLayouts for the windows extant at application
@@ -557,16 +553,14 @@ class TasksApplicationState(HasStrictTraits):
     version = Int(1)
 
     def get_equivalent_window_layout(self, window_layout):
-        """ Gets an equivalent TaskWindowLayout, if there is one.
-        """
+        """Gets an equivalent TaskWindowLayout, if there is one."""
         for layout in self.window_layouts:
             if layout.is_equivalent_to(window_layout):
                 return layout
         return None
 
     def get_task_layout(self, task_id):
-        """ Gets a TaskLayout with the specified ID, there is one.
-        """
+        """Gets a TaskLayout with the specified ID, there is one."""
         for window_layout in self.window_layouts:
             for layout in window_layout.items:
                 if layout.id == task_id:
@@ -574,8 +568,7 @@ def get_task_layout(self, task_id):
         return None
 
     def push_window_layout(self, window_layout):
-        """ Merge a TaskWindowLayout into the accumulated list.
-        """
+        """Merge a TaskWindowLayout into the accumulated list."""
         self.window_layouts = [
             layout
             for layout in self.window_layouts
diff --git a/envisage/ui/tasks/tasks_plugin.py b/envisage/ui/tasks/tasks_plugin.py
index b128ce668..68720cd66 100644
--- a/envisage/ui/tasks/tasks_plugin.py
+++ b/envisage/ui/tasks/tasks_plugin.py
@@ -8,9 +8,10 @@
 #
 # Thanks for using Enthought open source!
 # Enthought library imports.
-from envisage.api import ExtensionPoint, Plugin, ServiceOffer
 from traits.api import Callable, Instance, List
 
+from envisage.api import ExtensionPoint, Plugin, ServiceOffer
+
 # Local imports.
 from .preferences_category import PreferencesCategory
 
@@ -19,7 +20,7 @@
 
 
 class TasksPlugin(Plugin):
-    """ The Envisage Tasks plugin.
+    """The Envisage Tasks plugin.
 
     The Tasks plugin uses Pyface Tasks to provide an extensible framework for
     building user interfaces. For more information, see the Tasks User Manual.
@@ -126,10 +127,11 @@ def _my_service_offers_default(self):
     my_task_extensions = List(contributes_to=TASK_EXTENSIONS)
 
     def _my_task_extensions_default(self):
+        from pyface.tasks.action.api import DockPaneToggleGroup, SchemaAddition
+
         from .action.exit_action import ExitAction
         from .action.preferences_action import PreferencesGroup
         from .task_extension import TaskExtension
-        from pyface.tasks.action.api import DockPaneToggleGroup, SchemaAddition
 
         actions = [
             SchemaAddition(id="Exit", factory=ExitAction, path="MenuBar/File"),
@@ -150,8 +152,7 @@ def _my_task_extensions_default(self):
     ###########################################################################
 
     def _create_preferences_dialog_service(self):
-        """ Factory method for preferences dialog service.
-        """
+        """Factory method for preferences dialog service."""
         from .preferences_dialog import PreferencesDialog
 
         dialog = PreferencesDialog(application=self.application)
diff --git a/envisage/ui/tasks/tests/data/create_pickles.py b/envisage/ui/tasks/tests/data/create_pickles.py
index 7cc471777..89cd62682 100644
--- a/envisage/ui/tasks/tests/data/create_pickles.py
+++ b/envisage/ui/tasks/tests/data/create_pickles.py
@@ -19,9 +19,10 @@
 import pathlib
 import pickle
 
-from envisage.ui.tasks.api import TasksApplicationState
 from pyface.tasks.api import TaskWindowLayout
 
+from envisage.ui.tasks.api import TasksApplicationState
+
 state = TasksApplicationState(
     version=1,
     window_layouts=[],
diff --git a/envisage/ui/tasks/tests/test_tasks_application.py b/envisage/ui/tasks/tests/test_tasks_application.py
index 8062fc0ae..73a59a685 100644
--- a/envisage/ui/tasks/tests/test_tasks_application.py
+++ b/envisage/ui/tasks/tests/test_tasks_application.py
@@ -16,6 +16,7 @@
 import unittest
 
 import pkg_resources
+
 from pyface.gui import GUI
 from pyface.i_gui import IGUI
 from traits.api import Event, HasTraits, provides
@@ -100,7 +101,8 @@ def test_layout_save_with_protocol_3(self):
 
         # Create application, and set it up to exit as soon as it's launched.
         app = TasksApplication(
-            state_location=state_location, layout_save_protocol=3,
+            state_location=state_location,
+            layout_save_protocol=3,
         )
         app.on_trait_change(app.exit, "application_initialized")
 
@@ -174,7 +176,8 @@ def test_layout_load_pickle_protocol_3(self):
 
         # Use a non-standard filename, to exercise that machinery.
         app = TasksApplication(
-            state_location=state_location, state_filename="fancy_state.pkl",
+            state_location=state_location,
+            state_filename="fancy_state.pkl",
         )
         app.on_trait_change(app.exit, "application_initialized")
         app.run()
diff --git a/envisage/ui/workbench/action/about_action.py b/envisage/ui/workbench/action/about_action.py
index 34c411c2c..21d03a385 100644
--- a/envisage/ui/workbench/action/about_action.py
+++ b/envisage/ui/workbench/action/about_action.py
@@ -15,7 +15,7 @@
 
 
 class AboutAction(Action):
-    """ An action that shows the 'About' dialog. """
+    """An action that shows the 'About' dialog."""
 
     #### 'Action' interface ###################################################
 
@@ -33,6 +33,6 @@ class AboutAction(Action):
     ###########################################################################
 
     def perform(self, event):
-        """ Perform the action. """
+        """Perform the action."""
 
         self.window.application.about()
diff --git a/envisage/ui/workbench/action/edit_preferences_action.py b/envisage/ui/workbench/action/edit_preferences_action.py
index dc455d8f7..07ba580c8 100644
--- a/envisage/ui/workbench/action/edit_preferences_action.py
+++ b/envisage/ui/workbench/action/edit_preferences_action.py
@@ -10,13 +10,14 @@
 """ An action that displays the preferences dialog. """
 
 
+from pyface.action.api import Action
+
 # Enthought library imports.
 from pyface.api import ImageResource
-from pyface.action.api import Action
 
 
 class EditPreferencesAction(Action):
-    """ An action that displays the preferences dialog. """
+    """An action that displays the preferences dialog."""
 
     #### 'Action' interface ###################################################
 
@@ -37,7 +38,7 @@ class EditPreferencesAction(Action):
     ###########################################################################
 
     def perform(self, event):
-        """ Performs the action. """
+        """Performs the action."""
 
         from apptools.preferences.ui.api import PreferencesManager
 
diff --git a/envisage/ui/workbench/action/exit_action.py b/envisage/ui/workbench/action/exit_action.py
index c64224664..cc1ea1490 100644
--- a/envisage/ui/workbench/action/exit_action.py
+++ b/envisage/ui/workbench/action/exit_action.py
@@ -10,13 +10,14 @@
 """ An action that exits the workbench. """
 
 
+from pyface.action.api import Action
+
 # Enthought library imports.
 from pyface.api import ImageResource
-from pyface.action.api import Action
 
 
 class ExitAction(Action):
-    """ An action that exits the workbench. """
+    """An action that exits the workbench."""
 
     #### 'Action' interface ###################################################
 
@@ -37,6 +38,6 @@ class ExitAction(Action):
     ###########################################################################
 
     def perform(self, event):
-        """ Perform the action. """
+        """Perform the action."""
 
         self.window.application.exit()
diff --git a/envisage/ui/workbench/default_action_set.py b/envisage/ui/workbench/default_action_set.py
index 89795b433..444724efe 100644
--- a/envisage/ui/workbench/default_action_set.py
+++ b/envisage/ui/workbench/default_action_set.py
@@ -13,13 +13,12 @@
 # Enthought library imports.
 from envisage.ui.action.api import Action, ActionSet, Group, Menu
 
-
 # This module's package.
 PKG = ".".join(__name__.split(".")[:-1])
 
 
 class DefaultActionSet(ActionSet):
-    """ The default workbench action set. """
+    """The default workbench action set."""
 
     menus = [
         Menu(
@@ -29,7 +28,7 @@ class DefaultActionSet(ActionSet):
                 Group(id="OpenGroup"),
                 Group(id="SaveGroup"),
                 Group(id="ImportGroup"),
-                Group(id="ExitGroup")
+                Group(id="ExitGroup"),
             ],
         ),
         Menu(
@@ -37,13 +36,11 @@ class DefaultActionSet(ActionSet):
             class_name="pyface.workbench.action.api:ViewMenuManager",
         ),
         Menu(
-            name="&Tools", path="MenuBar",
-            groups=[Group(id="PreferencesGroup")]
-        ),
-        Menu(
-            name="&Help", path="MenuBar",
-            groups=[Group(id="AboutGroup")]
+            name="&Tools",
+            path="MenuBar",
+            groups=[Group(id="PreferencesGroup")],
         ),
+        Menu(name="&Help", path="MenuBar", groups=[Group(id="AboutGroup")]),
     ]
 
     actions = [
diff --git a/envisage/ui/workbench/workbench.py b/envisage/ui/workbench/workbench.py
index 68b877e5f..e7ac23f84 100644
--- a/envisage/ui/workbench/workbench.py
+++ b/envisage/ui/workbench/workbench.py
@@ -12,18 +12,18 @@
 
 # Enthought library imports.
 import pyface.workbench.api as pyface
-
-from envisage.api import IApplication
 from pyface.api import YES
 from traits.api import Delegate, Instance
 
+from envisage.api import IApplication
+
 # Local imports.
 from .workbench_preferences import WorkbenchPreferences
 from .workbench_window import WorkbenchWindow
 
 
 class Workbench(pyface.Workbench):
-    """ The Envisage workbench.
+    """The Envisage workbench.
 
     There is (usually) exactly *one* workbench per application. The workbench
     can create any number of workbench windows.
@@ -53,7 +53,7 @@ class Workbench(pyface.Workbench):
     ###########################################################################
 
     def _exiting_changed(self, event):
-        """ Called when the workbench is exiting. """
+        """Called when the workbench is exiting."""
 
         if self.prompt_on_exit:
             answer = self.active_window.confirm(
diff --git a/envisage/ui/workbench/workbench_action_manager_builder.py b/envisage/ui/workbench/workbench_action_manager_builder.py
index 3efc2462f..d8f0dd310 100644
--- a/envisage/ui/workbench/workbench_action_manager_builder.py
+++ b/envisage/ui/workbench/workbench_action_manager_builder.py
@@ -13,17 +13,17 @@
 # Standard library imports.
 import weakref
 
-# Enthought library imports.
-from envisage.ui.action.api import AbstractActionManagerBuilder
 from pyface.action.api import Action, Group, MenuManager
-from pyface.workbench.action.api import MenuBarManager
-from pyface.workbench.action.api import ToolBarManager
+from pyface.workbench.action.api import MenuBarManager, ToolBarManager
 from traits.api import Any, Instance
 
+# Enthought library imports.
+from envisage.ui.action.api import AbstractActionManagerBuilder
 
-class WorkbenchActionManagerBuilder(AbstractActionManagerBuilder):
-    """ The action manager builder used to build the workbench menu/tool bars.
 
+class WorkbenchActionManagerBuilder(AbstractActionManagerBuilder):
+    """
+    The action manager builder used to build the workbench menu/tool bars.
     """
 
     #### 'WorkbenchActionManagerBuilder' interface ############################
@@ -41,7 +41,7 @@ class WorkbenchActionManagerBuilder(AbstractActionManagerBuilder):
     ###########################################################################
 
     def _create_action(self, definition):
-        """ Create an action implementation from an action definition. """
+        """Create an action implementation from an action definition."""
 
         traits = {"window": self.window}
 
@@ -69,7 +69,7 @@ def _create_action(self, definition):
         return action
 
     def _create_group(self, definition):
-        """ Create a group implementation from a group definition. """
+        """Create a group implementation from a group definition."""
 
         traits = {}
 
@@ -93,7 +93,7 @@ def _create_group(self, definition):
         return group
 
     def _create_menu_manager(self, definition):
-        """ Create a menu manager implementation from a menu definition. """
+        """Create a menu manager implementation from a menu definition."""
 
         # fixme: 'window' is not actually a trait on 'MenuManager'! We set
         # it here to allow the 'View' menu to be created. However, it seems
@@ -129,12 +129,12 @@ def _create_menu_manager(self, definition):
         return menu_manager
 
     def _create_menu_bar_manager(self):
-        """ Create a menu bar manager from the builder's action sets. """
+        """Create a menu bar manager from the builder's action sets."""
 
         return MenuBarManager(window=self.window)
 
     def _create_tool_bar_manager(self, definition):
-        """ Create a tool bar manager implementation from a definition. """
+        """Create a tool bar manager implementation from a definition."""
 
         traits = {"window": self.window, "show_tool_names": False}
 
@@ -173,11 +173,11 @@ def _create_tool_bar_manager(self, definition):
     ###########################################################################
 
     def __actions_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return weakref.WeakValueDictionary()
 
     def _import_symbol(self, symbol_path):
-        """ Import a symbol. """
+        """Import a symbol."""
 
         return self.window.application.import_symbol(symbol_path)
diff --git a/envisage/ui/workbench/workbench_action_set.py b/envisage/ui/workbench/workbench_action_set.py
index 91880aeb7..43e2fc6cd 100644
--- a/envisage/ui/workbench/workbench_action_set.py
+++ b/envisage/ui/workbench/workbench_action_set.py
@@ -10,13 +10,14 @@
 """ An action set in a workbench window. """
 
 
+from traits.api import Instance, List, Str
+
 # Enthought library imports.
 from envisage.ui.action.api import ActionSet
-from traits.api import Instance, List, Str
 
 
 class WorkbenchActionSet(ActionSet):
-    """ An action set in a workbench window.
+    """An action set in a workbench window.
 
     This class adds a 'window' trait which is the workbench window that the
     action set is in. The trait is set by the framework when the action set is
@@ -62,14 +63,14 @@ class WorkbenchActionSet(ActionSet):
     ###########################################################################
 
     def _enabled_changed(self, trait_name, old, new):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         if self.window is not None:
             self._update_tool_bars(self.window, "enabled", new)
             self._update_actions(self.window, "enabled", new)
 
     def _visible_changed(self, trait_name, old, new):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         if self.window is not None:
             self._update_tool_bars(self.window, "visible", new)
@@ -80,7 +81,7 @@ def _visible_changed(self, trait_name, old, new):
     ###########################################################################
 
     def initialize(self):
-        """ Called when the action set has been added to a window.
+        """Called when the action set has been added to a window.
 
         Use this method to hook up any listeners that you need to control
         the enabled and/or visible state of the action set.
@@ -105,7 +106,7 @@ def initialize(self):
     #### Trait change handlers ################################################
 
     def _window_changed(self):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         # fixme: We put the code into an 'initialize' method because it seems
         # easier to explain that we expect it to be overridden. It seems a bit
@@ -115,7 +116,7 @@ def _window_changed(self):
     #### Methods ##############################################################
 
     def _refresh(self):
-        """ Refresh the enabled/visible state of the action set. """
+        """Refresh the enabled/visible state of the action set."""
 
         window = self.window
 
@@ -150,10 +151,10 @@ def _refresh(self):
             )
 
     def _update_actions(self, window, trait_name, value):
-        """ Update the state of the tool bars in the action set. """
+        """Update the state of the tool bars in the action set."""
 
         def visitor(item):
-            """ Called when we visit each item in an action manager. """
+            """Called when we visit each item in an action manager."""
 
             # fixme: The 'additions' group gets created by default and hence
             # has no '_action_set_' attribute. This smells because of the fact
@@ -172,7 +173,7 @@ def visitor(item):
             tool_bar_manager.walk(visitor)
 
     def _update_tool_bars(self, window, trait_name, value):
-        """ Update the state of the tool bars in the action set. """
+        """Update the state of the tool bars in the action set."""
 
         for tool_bar_manager in window.tool_bar_managers:
             if tool_bar_manager._action_set_ is self:
diff --git a/envisage/ui/workbench/workbench_application.py b/envisage/ui/workbench/workbench_application.py
index f56b47979..3ef0b44b6 100644
--- a/envisage/ui/workbench/workbench_application.py
+++ b/envisage/ui/workbench/workbench_application.py
@@ -13,23 +13,22 @@
 # Standard library imports.
 import logging
 
-# Enthought library imports.
-from envisage.api import Application
-from pyface.api import AboutDialog, Dialog, GUI, ImageResource
-from pyface.api import SplashScreen
+from pyface.api import AboutDialog, Dialog, GUI, ImageResource, SplashScreen
 from pyface.workbench.api import IWorkbench
 from traits.api import Callable, Instance, Str, Tuple
 
+# Enthought library imports.
+from envisage.api import Application
+
 # Local imports.
 from .workbench import Workbench
 
-
 # Logging.
 logger = logging.getLogger(__name__)
 
 
 class WorkbenchApplication(Application):
-    """ The entry point for an Envisage Workbench application.
+    """The entry point for an Envisage Workbench application.
 
     i.e. a GUI application whose user interface is provided by the workbench
     plugin.
@@ -80,7 +79,7 @@ class WorkbenchApplication(Application):
     ###########################################################################
 
     def run(self):
-        """ Run the application.
+        """Run the application.
 
         This does the following (so you don't have to ;^):-
 
@@ -120,24 +119,24 @@ def run(self):
     #### Initializers #########################################################
 
     def _about_dialog_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return AboutDialog(image=ImageResource("about"))
 
     def _gui_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return GUI(splash_screen=self.splash_screen)
 
     def _workbench_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return self.create_workbench()
 
     #### Methods ##############################################################
 
     def about(self):
-        """ Display the about dialog. """
+        """Display the about dialog."""
 
         # fixme: We really need to create a new 'about dialog' every time so
         # that it can have the active window as its parent.
@@ -146,14 +145,14 @@ def about(self):
     # fixme: Is this needed on the public API? Why can't we just do this in
     # the default initializer (_workbench_default)?
     def create_workbench(self):
-        """ Create the workbench. """
+        """Create the workbench."""
 
         logger.debug("workbench factory %s", self.workbench_factory)
 
         return self.workbench_factory(application=self)
 
     def exit(self):
-        """ Exit the application.
+        """Exit the application.
 
         This closes all open windows and hence exits the GUI event loop.
 
@@ -166,7 +165,7 @@ def exit(self):
     ###########################################################################
 
     def _on_workbench_exited(self):
-        """ Dynamic trait change handler. """
+        """Dynamic trait change handler."""
 
         # We don't invoke 'stop' directly because:-
         #
diff --git a/envisage/ui/workbench/workbench_editor_manager.py b/envisage/ui/workbench/workbench_editor_manager.py
index 603676b42..ee81276e5 100644
--- a/envisage/ui/workbench/workbench_editor_manager.py
+++ b/envisage/ui/workbench/workbench_editor_manager.py
@@ -14,14 +14,14 @@
 
 
 class WorkbenchEditorManager(EditorManager):
-    """ An editor manager that uses contributed editors. """
+    """An editor manager that uses contributed editors."""
 
     ###########################################################################
     # 'IEditorManager' interface.
     ###########################################################################
 
     def create_editor(self, window, obj, kind):
-        """ Create an editor for an object.
+        """Create an editor for an object.
 
         For now, the 'kind' is actually a factory that produces editors. It
         should be a callable with the following signature::
@@ -43,7 +43,7 @@ def create_editor(self, window, obj, kind):
     ###########################################################################
 
     def _is_editing(self, editor, obj, kind):
-        """ Return True if the editor is editing the object. """
+        """Return True if the editor is editing the object."""
 
         if kind is None:
             kind = TraitsUIEditor
diff --git a/envisage/ui/workbench/workbench_plugin.py b/envisage/ui/workbench/workbench_plugin.py
index c5f2d654a..4bc3a3571 100644
--- a/envisage/ui/workbench/workbench_plugin.py
+++ b/envisage/ui/workbench/workbench_plugin.py
@@ -10,17 +10,17 @@
 """ The Envisage workbench plugin. """
 
 
-# Enthought library imports.
-from envisage.api import ExtensionPoint, Plugin, ServiceOffer
 from traits.api import Callable, List
 
+# Enthought library imports.
+from envisage.api import ExtensionPoint, Plugin, ServiceOffer
 
 # This module's package.
 PKG = ".".join(__name__.split(".")[:-1])
 
 
 class WorkbenchPlugin(Plugin):
-    """ The Envisage workbench plugin.
+    """The Envisage workbench plugin.
 
     The workbench plugin uses the Pyface workbench to provide the basis of an
     IDE-like user interface. The interface is made up of perspectives, views
@@ -180,7 +180,7 @@ def foo_view_factory(**traits):
     my_action_sets = List(contributes_to=ACTION_SETS)
 
     def _my_action_sets_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         from .default_action_set import DefaultActionSet
 
@@ -189,14 +189,14 @@ def _my_action_sets_default(self):
     my_preferences = List(contributes_to=PREFERENCES)
 
     def _my_preferences_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return ["pkgfile://envisage.ui.workbench/preferences.ini"]
 
     my_preferences_pages = List(contributes_to=PREFERENCES_PAGES)
 
     def _my_preferences_pages_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         from .workbench_preferences_page import WorkbenchPreferencesPage
 
@@ -205,7 +205,7 @@ def _my_preferences_pages_default(self):
     my_service_offers = List(contributes_to=SERVICE_OFFERS)
 
     def _my_service_offers_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         preferences_manager_service_offer = ServiceOffer(
             protocol="apptools.preferences.ui.preferences_manager"
@@ -225,7 +225,7 @@ def _my_service_offers_default(self):
     ###########################################################################
 
     def _create_preferences_manager_service(self, **properties):
-        """ Factory method for the preferences manager service. """
+        """Factory method for the preferences manager service."""
 
         from apptools.preferences.ui.api import PreferencesManager
 
@@ -236,7 +236,7 @@ def _create_preferences_manager_service(self, **properties):
         return preferences_manager
 
     def _create_workbench_service(self, **properties):
-        """ Factory method for the workbench service. """
+        """Factory method for the workbench service."""
 
         # We don't actually create the workbench here, we just return a
         # reference to it.
diff --git a/envisage/ui/workbench/workbench_preferences.py b/envisage/ui/workbench/workbench_preferences.py
index 1d9b9be91..06ddce586 100644
--- a/envisage/ui/workbench/workbench_preferences.py
+++ b/envisage/ui/workbench/workbench_preferences.py
@@ -16,7 +16,7 @@
 
 
 class WorkbenchPreferences(PreferencesHelper):
-    """ Helper for the workbench preferences. """
+    """Helper for the workbench preferences."""
 
     #### 'PreferencesHelper' interface ########################################
 
diff --git a/envisage/ui/workbench/workbench_preferences_page.py b/envisage/ui/workbench/workbench_preferences_page.py
index c945e0044..8288f6819 100644
--- a/envisage/ui/workbench/workbench_preferences_page.py
+++ b/envisage/ui/workbench/workbench_preferences_page.py
@@ -17,7 +17,7 @@
 
 
 class WorkbenchPreferencesPage(PreferencesPage):
-    """ The main preferences page for the workbench. """
+    """The main preferences page for the workbench."""
 
     #### 'PreferencesPage' interface ##########################################
 
diff --git a/envisage/ui/workbench/workbench_window.py b/envisage/ui/workbench/workbench_window.py
index 4ff8a509f..225a1df60 100644
--- a/envisage/ui/workbench/workbench_window.py
+++ b/envisage/ui/workbench/workbench_window.py
@@ -15,26 +15,29 @@
 
 # Enthought library imports.
 import pyface.workbench.api as pyface
-
-from envisage.api import IExtensionPointUser, IExtensionRegistry
-from envisage.api import IServiceRegistry
-from envisage.api import ExtensionPoint, ServiceRegistry
-from envisage.ui.action.api import ActionSet
 from pyface.action.api import StatusBarManager
 from traits.api import Delegate, Instance, List, Property, provides
 
+from envisage.api import (
+    ExtensionPoint,
+    IExtensionPointUser,
+    IExtensionRegistry,
+    IServiceRegistry,
+    ServiceRegistry,
+)
+from envisage.ui.action.api import ActionSet
+
 # Local imports.
 from .workbench_action_manager_builder import WorkbenchActionManagerBuilder
 from .workbench_editor_manager import WorkbenchEditorManager
 
-
 # Logging.
 logger = logging.getLogger(__name__)
 
 
 @provides(IServiceRegistry, IExtensionPointUser)
 class WorkbenchWindow(pyface.WorkbenchWindow):
-    """ An extensible workbench window. """
+    """An extensible workbench window."""
 
     # Extension point Ids.
     ACTION_SETS = "envisage.ui.workbench.action_sets"
@@ -90,7 +93,7 @@ class WorkbenchWindow(pyface.WorkbenchWindow):
     ###########################################################################
 
     def _get_extension_registry(self):
-        """ Trait property getter. """
+        """Trait property getter."""
 
         return self.application
 
@@ -101,29 +104,29 @@ def _get_extension_registry(self):
     #### Trait initializers ###################################################
 
     def _menu_bar_manager_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return self._action_manager_builder.create_menu_bar_manager("MenuBar")
 
     def _status_bar_manager_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return StatusBarManager()
 
     def _tool_bar_managers_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return self._action_manager_builder.create_tool_bar_managers("ToolBar")
 
     #### Trait change handlers ################################################
 
     def _opening_changed(self):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         self._service_ids = self._register_service_offers(self._service_offers)
 
     def _closed_changed(self):
-        """ Static trait change handler. """
+        """Static trait change handler."""
 
         self._unregister_service_offers(self._service_ids)
 
@@ -134,27 +137,27 @@ def _closed_changed(self):
     #### Trait initializers ###################################################
 
     def _editor_manager_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return WorkbenchEditorManager(window=self)
 
     def _icon_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return self.workbench.application.icon
 
     def _perspectives_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return [factory() for factory in self._perspectives]
 
     def _title_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return self.workbench.application.name
 
     def _views_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return [factory(window=self) for factory in self._views]
 
@@ -163,7 +166,7 @@ def _views_default(self):
     ###########################################################################
 
     def _action_sets_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         return [factory(window=self) for factory in self._action_sets]
 
@@ -172,7 +175,7 @@ def _action_sets_default(self):
     ###########################################################################
 
     def get_service(self, protocol, query="", minimize="", maximize=""):
-        """ Return at most one service that matches the specified query. """
+        """Return at most one service that matches the specified query."""
 
         service = self.service_registry.get_service(
             protocol, query, minimize, maximize
@@ -181,12 +184,12 @@ def get_service(self, protocol, query="", minimize="", maximize=""):
         return service
 
     def get_service_properties(self, service_id):
-        """ Return the dictionary of properties associated with a service. """
+        """Return the dictionary of properties associated with a service."""
 
         return self.service_registry.get_service_properties(service_id)
 
     def get_services(self, protocol, query="", minimize="", maximize=""):
-        """ Return all services that match the specified query. """
+        """Return all services that match the specified query."""
 
         services = self.service_registry.get_services(
             protocol, query, minimize, maximize
@@ -195,7 +198,7 @@ def get_services(self, protocol, query="", minimize="", maximize=""):
         return services
 
     def register_service(self, protocol, obj, properties=None):
-        """ Register a service. """
+        """Register a service."""
 
         service_id = self.service_registry.register_service(
             protocol, obj, properties
@@ -204,12 +207,12 @@ def register_service(self, protocol, obj, properties=None):
         return service_id
 
     def set_service_properties(self, service_id, properties):
-        """ Set the dictionary of properties associated with a service. """
+        """Set the dictionary of properties associated with a service."""
 
         self.service_registry.set_service_properties(service_id, properties)
 
     def unregister_service(self, service_id):
-        """ Unregister a service. """
+        """Unregister a service."""
 
         self.service_registry.unregister_service(service_id)
 
@@ -218,7 +221,7 @@ def unregister_service(self, service_id):
     ###########################################################################
 
     def __action_manager_builder_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         action_manager_builder = WorkbenchActionManagerBuilder(
             window=self, action_sets=self.action_sets
@@ -227,12 +230,12 @@ def __action_manager_builder_default(self):
         return action_manager_builder
 
     def _register_service_offers(self, service_offers):
-        """ Register all service offers. """
+        """Register all service offers."""
 
         return list(map(self._register_service_offer, service_offers))
 
     def _register_service_offer(self, service_offer):
-        """ Register a service offer. """
+        """Register a service offer."""
 
         # Add the window to the service offer properties (this is so that it
         # is available to the factory when it is called to create the actual
@@ -248,7 +251,7 @@ def _register_service_offer(self, service_offer):
         return service_id
 
     def _unregister_service_offers(self, service_ids):
-        """ Unregister all service offers. """
+        """Unregister all service offers."""
 
         # Unregister the services in the reverse order that we registered
         # them.
diff --git a/envisage/unknown_extension.py b/envisage/unknown_extension.py
index e49ce0303..f5ee969c6 100644
--- a/envisage/unknown_extension.py
+++ b/envisage/unknown_extension.py
@@ -11,4 +11,4 @@
 
 
 class UnknownExtension(Exception):
-    """ The exception raised when an unknown extension is referenced. """
+    """The exception raised when an unknown extension is referenced."""
diff --git a/envisage/unknown_extension_point.py b/envisage/unknown_extension_point.py
index 0b5eac9ec..617009a26 100644
--- a/envisage/unknown_extension_point.py
+++ b/envisage/unknown_extension_point.py
@@ -11,4 +11,4 @@
 
 
 class UnknownExtensionPoint(Exception):
-    """ The exception raised when an unknown extension point is referenced. """
+    """The exception raised when an unknown extension point is referenced."""
diff --git a/etstool.py b/etstool.py
index d7d511643..efd51fc8d 100644
--- a/etstool.py
+++ b/etstool.py
@@ -106,8 +106,6 @@
     "apptools",
     "coverage",
     "enthought_sphinx_theme",
-    "flake8",
-    "flake8_ets",
     "pyface",
     "sphinx",
     "sphinx_copybutton",
@@ -116,7 +114,14 @@
 }
 
 # Dependencies we install from PyPI
-pypi_dependencies = {}
+pypi_dependencies = {
+    # style packages; install from PyPI to make sure that we're compatible
+    # with the style checks used in the check-style.yml workflow
+    "black~=23.0",
+    "flake8",
+    "flake8-ets",
+    "isort",
+}
 
 # Dependencies we install from source for cron tests
 # Order from packages with the most dependencies to one with the least
@@ -187,6 +192,16 @@ def cli():
     pass
 
 
+# Subgroup for checking and fixing style
+
+
+@cli.group()
+def style():
+    """
+    Commands for checking style and applying style fixes.
+    """
+
+
 @cli.command()
 @edm_option
 @runtime_option
@@ -195,9 +210,7 @@ def cli():
 @editable_option
 @source_option
 def install(edm, runtime, toolkit, environment, editable, source):
-    """ Install project and dependencies into a clean EDM environment.
-
-    """
+    """Install project and dependencies into a clean EDM environment."""
     parameters = get_parameters(edm, runtime, toolkit, environment)
     packages = " ".join(
         dependencies
@@ -264,7 +277,7 @@ def install(edm, runtime, toolkit, environment, editable, source):
 @toolkit_option
 @environment_option
 def shell(edm, runtime, toolkit, environment):
-    """ Create a shell into the EDM development environment
+    """Create a shell into the EDM development environment
     (aka 'activate' it).
 
     """
@@ -275,17 +288,41 @@ def shell(edm, runtime, toolkit, environment):
     execute(commands, parameters)
 
 
-@cli.command()
+@style.command(name="check")
 @edm_option
 @runtime_option
 @toolkit_option
 @environment_option
-def flake8(edm, runtime, toolkit, environment):
-    """ Run a flake8 check in a given environment.
+def style_check(edm, runtime, toolkit, environment):
+    """
+    Run style checks.
+    """
+    parameters = get_parameters(edm, runtime, toolkit, environment)
+    commands = [
+        "{edm} run -e {environment} -- python -m black --check --diff .",
+        "{edm} run -e {environment} -- python -m isort --check --diff .",
+        "{edm} run -e {environment} -- python -m flake8 .",
+    ]
+    execute(commands, parameters)
 
+
+@style.command(name="fix")
+@edm_option
+@runtime_option
+@toolkit_option
+@environment_option
+def style_fix(edm, runtime, toolkit, environment):
+    """
+    Run style fixers.
+
+    This automatically fixes any black or isort failures, but it won't
+    automatically fix all flake8 errors.
     """
     parameters = get_parameters(edm, runtime, toolkit, environment)
-    commands = ["{edm} run -e {environment} -- python -m flake8"]
+    commands = [
+        "{edm} run -e {environment} -- python -m black .",
+        "{edm} run -e {environment} -- python -m isort .",
+    ]
     execute(commands, parameters)
 
 
@@ -295,9 +332,7 @@ def flake8(edm, runtime, toolkit, environment):
 @toolkit_option
 @environment_option
 def test(edm, runtime, toolkit, environment):
-    """ Run the test suite in a given environment with the specified toolkit.
-
-    """
+    """Run the test suite in a given environment with the specified toolkit."""
     parameters = get_parameters(edm, runtime, toolkit, environment)
     environ = dict(PYTHONUNBUFFERED="1")
     commands = [
@@ -324,9 +359,7 @@ def test(edm, runtime, toolkit, environment):
 @toolkit_option
 @environment_option
 def cleanup(edm, runtime, toolkit, environment):
-    """ Remove a development environment.
-
-    """
+    """Remove a development environment."""
     parameters = get_parameters(edm, runtime, toolkit, environment)
     commands = [
         "{edm} environments remove {environment} --purge -y",
@@ -341,9 +374,7 @@ def cleanup(edm, runtime, toolkit, environment):
 @runtime_option
 @toolkit_option
 def test_clean(edm, runtime, toolkit):
-    """ Run tests in a clean environment, cleaning up afterwards
-
-    """
+    """Run tests in a clean environment, cleaning up afterwards"""
     args = ["--toolkit={}".format(toolkit), "--runtime={}".format(runtime)]
     if edm is not None:
         args.append("--edm={}".format(edm))
@@ -362,9 +393,7 @@ def test_clean(edm, runtime, toolkit):
 @environment_option
 @editable_option
 def update(edm, runtime, toolkit, environment, editable):
-    """ Update/Reinstall package into environment.
-
-    """
+    """Update/Reinstall package into environment."""
     parameters = get_parameters(edm, runtime, toolkit, environment)
     if editable:
         install_cmd = (
@@ -385,9 +414,7 @@ def update(edm, runtime, toolkit, environment, editable):
 @cli.command()
 @edm_option
 def test_all(edm):
-    """ Run test_clean across all supported environment combinations.
-
-    """
+    """Run test_clean across all supported environment combinations."""
     failed_command = False
     for runtime, toolkits in supported_combinations.items():
         for toolkit in toolkits:
@@ -412,7 +439,7 @@ def test_all(edm):
 @toolkit_option
 @environment_option
 def docs(edm, runtime, toolkit, environment):
-    """ Build HTML documentation. """
+    """Build HTML documentation."""
 
     parameters = get_parameters(edm, runtime, toolkit, environment)
     parameters["docs_source"] = "docs/source"
@@ -422,9 +449,10 @@ def docs(edm, runtime, toolkit, environment):
 
     # Remove any previously autogenerated API documentation.
     doc_api_files = os.listdir(docs_source_api)
-    permanent = ['envisage.api.rst', 'templates']
-    previously_autogenerated = \
-        [file for file in doc_api_files if file not in permanent]
+    permanent = ["envisage.api.rst", "templates"]
+    previously_autogenerated = [
+        file for file in doc_api_files if file not in permanent
+    ]
     for file in previously_autogenerated:
         os.remove(os.path.join(docs_source_api, file))
 
@@ -443,8 +471,9 @@ def docs(edm, runtime, toolkit, environment):
 
 # Utility routines
 
+
 def get_parameters(edm, runtime, toolkit, environment):
-    """ Set up parameters dictionary for format() substitution """
+    """Set up parameters dictionary for format() substitution"""
 
     if edm is None:
         edm = locate_edm()
@@ -472,7 +501,7 @@ def get_parameters(edm, runtime, toolkit, environment):
 
 @contextmanager
 def do_in_tempdir(files=(), capture_files=()):
-    """ Create a temporary directory, cleaning up after done.
+    """Create a temporary directory, cleaning up after done.
 
     Creates the temporary directory, and changes into it.  On exit returns to
     original directory and removes temporary dir.
diff --git a/examples/legacy/workbench/AcmeLab/acme/acmelab/acmelab.py b/examples/legacy/workbench/AcmeLab/acme/acmelab/acmelab.py
index f6f804116..2eac099fe 100644
--- a/examples/legacy/workbench/AcmeLab/acme/acmelab/acmelab.py
+++ b/examples/legacy/workbench/AcmeLab/acme/acmelab/acmelab.py
@@ -14,13 +14,14 @@
 # Standard library imports.
 from logging import DEBUG
 
+from pyface.api import AboutDialog, ImageResource, SplashScreen
+
 # Enthought library imports.
 from envisage.ui.workbench.api import WorkbenchApplication
-from pyface.api import AboutDialog, ImageResource, SplashScreen
 
 
 class Acmelab(WorkbenchApplication):
-    """ The Acme Lab application. """
+    """The Acme Lab application."""
 
     #### 'IApplication' interface #############################################
 
@@ -42,7 +43,7 @@ class Acmelab(WorkbenchApplication):
     ###########################################################################
 
     def _about_dialog_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         about_dialog = AboutDialog(
             parent=self.workbench.active_window.control,
@@ -52,7 +53,7 @@ def _about_dialog_default(self):
         return about_dialog
 
     def _splash_screen_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         splash_screen = SplashScreen(
             image=ImageResource("splash"),
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/acme_preferences_page.py b/examples/legacy/workbench/AcmeLab/acme/workbench/acme_preferences_page.py
index e5bf6fba1..5d887258e 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/acme_preferences_page.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/acme_preferences_page.py
@@ -13,12 +13,12 @@
 
 # Enthought library imports.
 from apptools.preferences.ui.api import PreferencesPage
-from traits.api import Color, Int, Float, Font
+from traits.api import Color, Float, Font, Int
 from traitsui.api import View
 
 
 class AcmePreferencesPage(PreferencesPage):
-    """ The preferences page for the Acme workbench. """
+    """The preferences page for the Acme workbench."""
 
     #### 'PreferencesPage' interface ##########################################
 
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/acme_workbench_plugin.py b/examples/legacy/workbench/AcmeLab/acme/workbench/acme_workbench_plugin.py
index 4200cd648..65b06f130 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/acme_workbench_plugin.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/acme_workbench_plugin.py
@@ -11,13 +11,14 @@
 """ The AcmeLab Workbench plugin. """
 
 
+from traits.api import List
+
 # Enthought library imports.
 from envisage.api import Plugin
-from traits.api import List
 
 
 class AcmeWorkbenchPlugin(Plugin):
-    """ The AcmeLab Workbench plugin.
+    """The AcmeLab Workbench plugin.
 
     This plugin is part of the 'AcmeLab' example application.
 
@@ -43,7 +44,7 @@ class AcmeWorkbenchPlugin(Plugin):
     action_sets = List(contributes_to=ACTION_SETS)
 
     def _action_sets_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         from .example_action_set import ExampleActionSet
 
@@ -53,10 +54,12 @@ def _action_sets_default(self):
     perspectives = List(contributes_to=PERSPECTIVES)
 
     def _perspectives_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
-        from acme.workbench.perspective.api import FooPerspective
-        from acme.workbench.perspective.api import BarPerspective
+        from acme.workbench.perspective.api import (
+            BarPerspective,
+            FooPerspective,
+        )
 
         return [FooPerspective, BarPerspective]
 
@@ -64,7 +67,7 @@ def _perspectives_default(self):
     preferences_pages = List(contributes_to=PREFERENCES_PAGES)
 
     def _preferences_pages_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         from acme_preferences_page import AcmePreferencesPage
 
@@ -74,9 +77,14 @@ def _preferences_pages_default(self):
     views = List(contributes_to=VIEWS)
 
     def _views_default(self):
-        """ Trait initializer. """
-
-        from acme.workbench.view.api import BlackView, BlueView, GreenView
-        from acme.workbench.view.api import RedView, YellowView
+        """Trait initializer."""
+
+        from acme.workbench.view.api import (
+            BlackView,
+            BlueView,
+            GreenView,
+            RedView,
+            YellowView,
+        )
 
         return [BlackView, BlueView, GreenView, RedView, YellowView]
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/action/new_view_action.py b/examples/legacy/workbench/AcmeLab/acme/workbench/action/new_view_action.py
index 36d88ca4a..8a8f383ca 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/action/new_view_action.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/action/new_view_action.py
@@ -17,7 +17,7 @@
 
 
 class NewViewAction(Action):
-    """ An action that dynamically creates and adds a view. """
+    """An action that dynamically creates and adds a view."""
 
     #### 'Action' interface ###################################################
 
@@ -35,7 +35,7 @@ class NewViewAction(Action):
     ###########################################################################
 
     def perform(self, event):
-        """ Perform the action. """
+        """Perform the action."""
 
         # You can give the view a position... (it default to 'left')...
         view = View(id="my.view.fred", name="Fred", position="right")
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/example_action_set.py b/examples/legacy/workbench/AcmeLab/acme/workbench/example_action_set.py
index 2d6b6cfff..d81e92fa8 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/example_action_set.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/example_action_set.py
@@ -17,7 +17,7 @@
 
 
 class ExampleActionSet(WorkbenchActionSet):
-    """ An action test useful for testing. """
+    """An action test useful for testing."""
 
     #### 'ActionSet' interface ################################################
 
@@ -29,26 +29,17 @@ class ExampleActionSet(WorkbenchActionSet):
             name="&Test",
             path="MenuBar",
             before="Help",
-            groups=[
-                Group(id="XGroup"),
-                Group(id="YGroup")
-            ],
+            groups=[Group(id="XGroup"), Group(id="YGroup")],
         ),
         Menu(
             name="Foo",
             path="MenuBar/Test",
-            groups=[
-                Group(id="XGroup"),
-                Group(id="YGroup")
-            ],
+            groups=[Group(id="XGroup"), Group(id="YGroup")],
         ),
         Menu(
             name="Bar",
             path="MenuBar/Test",
-            groups=[
-                Group(id="XGroup"),
-                Group(id="YGroup")
-            ],
+            groups=[Group(id="XGroup"), Group(id="YGroup")],
         ),
     ]
 
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/perspective/bar_perspective.py b/examples/legacy/workbench/AcmeLab/acme/workbench/perspective/bar_perspective.py
index b76c89ee8..e06fc0343 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/perspective/bar_perspective.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/perspective/bar_perspective.py
@@ -16,7 +16,7 @@
 
 
 class BarPerspective(Perspective):
-    """ An example perspective. """
+    """An example perspective."""
 
     # The perspective's name.
     name = "Bar"
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/perspective/foo_perspective.py b/examples/legacy/workbench/AcmeLab/acme/workbench/perspective/foo_perspective.py
index 452bfff13..becea6af2 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/perspective/foo_perspective.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/perspective/foo_perspective.py
@@ -16,7 +16,7 @@
 
 
 class FooPerspective(Perspective):
-    """ An example perspective. """
+    """An example perspective."""
 
     # The perspective's name.
     name = "Foo"
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/view/black_view.py b/examples/legacy/workbench/AcmeLab/acme/workbench/view/black_view.py
index a00adc497..a78f46f8e 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/view/black_view.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/view/black_view.py
@@ -16,7 +16,7 @@
 
 
 class BlackView(ColorView):
-    """ A view containing a black panel! """
+    """A view containing a black panel!"""
 
     #### 'IView' interface ####################################################
 
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/view/blue_view.py b/examples/legacy/workbench/AcmeLab/acme/workbench/view/blue_view.py
index cc667cc11..74ef6e656 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/view/blue_view.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/view/blue_view.py
@@ -16,7 +16,7 @@
 
 
 class BlueView(ColorView):
-    """ A view containing a blue panel! """
+    """A view containing a blue panel!"""
 
     #### 'IView' interface ####################################################
 
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/view/color_view.py b/examples/legacy/workbench/AcmeLab/acme/workbench/view/color_view.py
index d643d72d0..371adbe51 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/view/color_view.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/view/color_view.py
@@ -11,10 +11,10 @@
 """ A view containing a colored panel! """
 
 
-# Enthought library imports.
-from traits.etsconfig.api import ETSConfig
 from pyface.workbench.api import View
 
+# Enthought library imports.
+from traits.etsconfig.api import ETSConfig
 
 _TOOLKIT_MAPPING = {
     "qt4": "qt",
@@ -22,14 +22,14 @@
 
 
 def _normalize_toolkit_name(toolkit):
-    """ Convert legacy toolkit names to current toolkit names. """
+    """Convert legacy toolkit names to current toolkit names."""
 
     toolkit = toolkit.lower()
     return _TOOLKIT_MAPPING.get(toolkit, toolkit)
 
 
 class ColorView(View):
-    """ A view containing a colored panel!
+    """A view containing a colored panel!
 
     This view is written so that it works with *both* wx and Qt4. Your own
     views obviously do not have to do this!
@@ -48,7 +48,7 @@ class ColorView(View):
     #### Trait initializers ###################################################
 
     def _id_default(self):
-        """ Trait initializer. """
+        """Trait initializer."""
 
         # By making the Id the same as the name, we make it easy to specify
         # the views in the example perspectives. Note for larger applications
@@ -59,7 +59,7 @@ def _id_default(self):
     #### Methods ##############################################################
 
     def create_control(self, parent):
-        """ Creates the toolkit-specific control that represents the view.
+        """Creates the toolkit-specific control that represents the view.
 
         'parent' is the toolkit-specific control that is the view's parent.
 
@@ -79,7 +79,7 @@ def create_control(self, parent):
     ###########################################################################
 
     def _wx_create_control(self, parent, color):
-        """ Create a wx version of the control. """
+        """Create a wx version of the control."""
 
         import wx
 
@@ -89,7 +89,7 @@ def _wx_create_control(self, parent, color):
         return panel
 
     def _qt_create_control(self, parent, color):
-        """ Create a Qt version of the control. """
+        """Create a Qt version of the control."""
 
         from pyface.qt import QtGui
 
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/view/green_view.py b/examples/legacy/workbench/AcmeLab/acme/workbench/view/green_view.py
index 8167fb829..85708a7bc 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/view/green_view.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/view/green_view.py
@@ -16,7 +16,7 @@
 
 
 class GreenView(ColorView):
-    """ A view containing a green panel! """
+    """A view containing a green panel!"""
 
     #### 'IView' interface ####################################################
 
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/view/red_view.py b/examples/legacy/workbench/AcmeLab/acme/workbench/view/red_view.py
index 2739973fb..4d55834a0 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/view/red_view.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/view/red_view.py
@@ -16,7 +16,7 @@
 
 
 class RedView(ColorView):
-    """ A view containing a red panel! """
+    """A view containing a red panel!"""
 
     #### 'IView' interface ####################################################
 
diff --git a/examples/legacy/workbench/AcmeLab/acme/workbench/view/yellow_view.py b/examples/legacy/workbench/AcmeLab/acme/workbench/view/yellow_view.py
index 2ac2e7e97..98c1289f9 100644
--- a/examples/legacy/workbench/AcmeLab/acme/workbench/view/yellow_view.py
+++ b/examples/legacy/workbench/AcmeLab/acme/workbench/view/yellow_view.py
@@ -16,7 +16,7 @@
 
 
 class YellowView(ColorView):
-    """ A view containing a yellow panel! """
+    """A view containing a yellow panel!"""
 
     #### 'IView' interface ####################################################
 
diff --git a/examples/legacy/workbench/AcmeLab/run.py b/examples/legacy/workbench/AcmeLab/run.py
index 2861f6f0c..edc1f1240 100644
--- a/examples/legacy/workbench/AcmeLab/run.py
+++ b/examples/legacy/workbench/AcmeLab/run.py
@@ -17,13 +17,12 @@
 # Example imports.
 from acme.acmelab.api import Acmelab
 
-# Enthought plugins.
-from envisage.api import CorePlugin
-from envisage.ui.workbench.workbench_plugin import WorkbenchPlugin
-
 # Example plugins.
 from acme.workbench.acme_workbench_plugin import AcmeWorkbenchPlugin
 
+# Enthought plugins.
+from envisage.api import CorePlugin
+from envisage.ui.workbench.workbench_plugin import WorkbenchPlugin
 
 # Do whatever you want to do with log messages! Here we create a log file.
 logger = logging.getLogger()
@@ -33,7 +32,7 @@
 
 
 def main():
-    """ Run the application. """
+    """Run the application."""
 
     # Create an application with the specified plugins.
     acmelab = Acmelab(