Fix some code quality and bug-risk issues (#817)

Author: pnijhara

pyls/plugins/jedi_completion.py

@@ -181,7 +181,7 @@ def _format_completion(d, include_params=True):
 def _label(definition):
     sig = definition.get_signatures()
     if definition.type in ('function', 'method') and sig:
-        params = ', '.join([param.name for param in sig[0].params])
+        params = ', '.join(param.name for param in sig[0].params)
         return '{}({})'.format(definition.name, params)
 
     return definition.name

pyls/workspace.py

@@ -98,7 +98,7 @@ def show_message(self, message, msg_type=lsp.MessageType.Info):
     def source_roots(self, document_path):
         """Return the source roots for the given document."""
         files = _utils.find_parents(self._root_path, document_path, ['setup.py', 'pyproject.toml']) or []
-        return list(set((os.path.dirname(project_file) for project_file in files))) or [self._root_path]
+        return list({os.path.dirname(project_file) for project_file in files}) or [self._root_path]
 
     def _create_document(self, doc_uri, source=None, version=None):
         path = uris.to_fs_path(doc_uri)