assertIsNone was introduced in Python3.1. Its use here should be replaced by

self.assertEquals(o.language, None)
to allow Python 2.X tests to run.

Author: rybesh

test/graph_case.py

@@ -290,7 +290,7 @@ def testStoreLiterals(self):
             elif o.value == u'こんにちは':
                 self.assertEquals(o.language, 'ja')
             elif o.value == u'something':
-                self.assertIsNone(o.language)
+                self.assertEquals(o.language, None)
             else:
                 self.fail()
         self.assertEquals(len(list(objs)), 3)