Use hacking 0.12.0
Use the new checks that are available:
[H106] Don’t put vim configuration in source files.
[H203] Use assertIs(Not)None to check for None.
[H904] Delay string interpolations at logging calls.
Fix code so tests pass.
Change-Id: If22ad272c332f30624ce10861408d377908b152b
Depends-On: I2aa44b62f900d4dfd67701b01eadd0523fbfaf07