This commit enables new flake8 checks:
* E265 block comment should start with '# '
* H405 multi line docstring summary not separated with an empty line
* E123 closing bracket does not match indentation of opening bracket's line
* H238 old style class declaration, use new style (inherit from `object`)
* E128 continuation line under-indented for visual indent
and makes related changes in the code.
Change-Id: Ie993afc930f6b74d7a990bcaa9fc0e9f5ba1585c
ec0f2dfd85