Following OpenStack Style Guidelines[1]:
[H203] Unit test assertions tend to give better messages for more
specific assertions. As a result, assertIsNotNone(...) is preferred
over assertNotEqual(None, ...) and assertIsNot(None, ...)
[1]http://docs.openstack.org/developer/hacking/#unit-tests-and-assertraises
Change-Id: Ie421629e0c78516595086510ba74130bfe6d1086