Using assertIsNone() instead of assertEqual(None)

Following OpenStack Style Guidelines:
[1] http://docs.openstack.org/developer/hacking/#unit-tests-and-assertraises
[H203] Unit test assertions tend to give better messages for more specific
assertions. As a result, assertIsNone(...) is preferred over
assertEqual(None, ...) and assertIs(..., None)

Change-Id: I378da84574fd06d873c72bb9b05cfe7da75c4cfe

tricircle/tests/unit/common/test_client.py

@@ -219,7 +219,7 @@ class ClientTest(unittest.TestCase):
         resource = self.client.create_resources(FAKE_RESOURCE, self.context,
                                                 'res3')
         # create_resources returns None by default
-        self.assertEqual(resource, None)
+        self.assertIsNone(resource)
 
     def test_resource_not_supported(self):
         # no such resource