Using assertIsNone() is preferred over assertEqual()

Following OpenStack Style Guidelines[1].
[H203] Unit test assertions tend to give better messages for more specific assertions.
As a result, assertIsNone(...) is preferred over assertEqual(None, ...)

[1] http://docs.openstack.org/developer/hacking/#dictionaries-lists

Change-Id: I46681aad0e7bae5c4b1f62db7987da24f516613d
1 file changed