Enable H702 PEP8 check

Fixes files with the PEP8 error:

    H702  Argument to _, _LI, _LW, _LC, or _LE must be just a string

and enables the PEP8 check in tox.ini.

Change-Id: I6ca187535981d9809ca221e90de38988601f96e0
Merge "Enable H702 PEP8 check"