Using assertIsNone() instead of assertIs(None)
Using assertIsNone() instead of assertIs(None)

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, ...) and assertIs(..,None)

[1]http://docs.openstack.org/developer/hacking/#unit-tests-and-assertraises

Change-Id: I3ec2fe6e967760dfd672d8a04329fe21ced81222

openstack/heat,openstack/heat,noironetworks/heat,noironetworks/heat