Fix check for pytest-marked extensions.

QuLogic · QuLogic · commit 05b88ad369a8 · 2017-05-23T01:41:17.000-04:00
All because of the mixed subplots test which marks one extension as
xfail. This was technically not checked correctly, but ended up with the
same result of the 'svg' extension being treated as xfail.
diff --git a/lib/matplotlib/testing/decorators.py b/lib/matplotlib/testing/decorators.py
@@ -223,7 +223,11 @@ def _xfail_if_format_is_uncomparable(extension):
 
 
 def _mark_xfail_if_format_is_uncomparable(extension):
-    will_fail = extension not in comparable_formats()
+    if isinstance(extension, six.string_types):
+        will_fail = extension not in comparable_formats()
+    else:
+        # Extension might be a pytest marker instead of a plain string.
+        will_fail = extension.args[0] not in comparable_formats()
     if will_fail:
         fail_msg = 'Cannot compare %s files on this system' % extension
         import pytest
