test: avoiding using assertIsNone in tests for compatibility with python 2.6
test: avoiding using assertIsNone in tests for compatibility with python 2.6

Former-commit-id: 3a5322ade7b1307543ddeb8875184f4c746eeb6a
tmfoltz/worldengine,MM1nd/worldengine,Mindwerks/worldengine,esampson/worldengine,sylvanmist/worldengine,sylvanmist/worldengine,Mindwerks/worldengine,esampson/worldengine,psi29a/worldengine,psi29a/worldengine,MM1nd/worldengine,tmfoltz/worldengine