Fix html5lib#237: fail if --update-xfail is used in wrong environment

Author: gsnedders

html5lib/tests/conftest.py

@@ -1,12 +1,14 @@
 import os.path
 
+import pkg_resources
 import pytest
 
 from .tree_construction import TreeConstructionFile
 from .tokenizer import TokenizerFile
 from .sanitizer import SanitizerFile
 
 _dir = os.path.abspath(os.path.dirname(__file__))
+_root = os.path.join(_dir, "..", "..")
 _testdata = os.path.join(_dir, "testdata")
 _tree_construction = os.path.join(_testdata, "tree-construction")
 _tokenizer = os.path.join(_testdata, "tokenizer")
@@ -15,15 +17,53 @@
 
 def pytest_configure(config):
     msgs = []
+
     if not os.path.exists(_testdata):
         msg = "testdata not available! "
-        if os.path.exists(os.path.join(_dir, "..", "..", ".git")):
+        if os.path.exists(os.path.join(_root, ".git")):
             msg += ("Please run git submodule update --init --recursive " +
                     "and then run tests again.")
         else:
             msg += ("The testdata doesn't appear to be included with this package, " +
                     "so finding the right version will be hard. :(")
         msgs.append(msg)
+
+    if config.option.update_xfail:
+        # Check for optional requirements
+        req_file = os.path.join(_root, "requirements-optional.txt")
+        if os.path.exists(req_file):
+            with open(req_file, "r") as fp:
+                for line in fp:
+                    if (line.strip() and
+                        not (line.startswith("-r") or
+                             line.startswith("#"))):
+                        if ";" in line:
+                            spec, marker = line.strip().split(";", 1)
+                        else:
+                            spec, marker = line.strip(), None
+                        req = pkg_resources.Requirement.parse(spec)
+                        if marker and not pkg_resources.evaluate_marker(marker):
+                            msgs.append("%s not available in this environment" % spec)
+                        else:
+                            try:
+                                installed = pkg_resources.working_set.find(req)
+                            except pkg_resources.VersionConflict:
+                                msgs.append("Outdated version of %s installed, need %s" % (req.name, spec))
+                            else:
+                                if not installed:
+                                    msgs.append("Need %s" % spec)
+
+        # Check cElementTree
+        import xml.etree.ElementTree as ElementTree
+
+        try:
+            import xml.etree.cElementTree as cElementTree
+        except ImportError:
+            msgs.append("cElementTree unable to be imported")
+        else:
+            if cElementTree.Element is ElementTree.Element:
+                msgs.append("cElementTree is just an alias for ElementTree")
+
     if msgs:
         pytest.exit("\n".join(msgs))