Fix test_optdb on python 2.6

theano/gof/tests/test_optdb.py

@@ -18,9 +18,9 @@ class Test_DB(TestCase):
 
         db.register('c', Opt(), 'z', 'asdf')
 
-        self.assertIn('a', db)
-        self.assertIn('b', db)
-        self.assertIn('c', db)
+        self.assertTrue('a' in db)
+        self.assertTrue('b' in db)
+        self.assertTrue('c' in db)
 
         try:
             db.register('c', Opt())  # name taken