Fix Python 3 error

alanbernstein · alanbernstein · commit 69e1092980e8 · 2017-01-01T19:21:30.000-06:00
diff --git a/lib/matplotlib/tests/test_style.py b/lib/matplotlib/tests/test_style.py
@@ -55,7 +55,7 @@ def test_deprecated_rc_warning_includes_filename():
             pass
 
     for w in warns:
-        assert basename in w.message.message
+        assert basename in str(w.message)
 
 
 def test_available():
