Move pep8 dependency into pep8 tox test
Move pep8 dependency into pep8 tox test

The other unit tests do not require pep8

Change-Id: I7ac68bb3ff48a76a6dd3db08a05827831069f141

enzochiau/cliff,dtroyer/cliff,enzochiau/cliff,openstack/cliff,idjaw/cliff,idjaw/cliff,varunarya10/cliff,dtroyer/cliff,varunarya10/cliff,openstack/cliff