Use flake8 instead pep8.

Change-Id: I9dd305cf06157094ea49b2f30cb8f1d28d170b8c
Renamed requirements files to standard names.

Change-Id: I439587c38c012653d6313e1860c9b8612a58d544
Merge "Use flake8 instead pep8."
Merge "Renamed requirements files to standard names."