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, ...)

Change-Id: I8cbac0ae6eeddd8d12c2652acff16a370f2066bb

tests/test_inventory.py

@@ -110,7 +110,7 @@ def get_inventory(clean=True, extra_args=None):
 class TestArgParser(unittest.TestCase):
     def test_no_args(self):
         arg_dict = dynamic_inventory.args([])
-        self.assertEqual(arg_dict['config'], None)
+        self.assertIsNone(arg_dict['config'])
         self.assertEqual(arg_dict['list'], False)
 
     def test_list_arg(self):