Remove old pep8, pyflakes and flake8 versions

The previous patch (Ia3495102a9d096c09802b9c079a8dc7ec1f65530) just
added new versions in order to not create a backwards incompatible
change, this removes the old versions and adds a new version of pep8 in
a backwards compatible way.

Change-Id: Ibdaa3724cceec8e53580ff2960a526fa54ec4b0a
Merge "Remove old pep8, pyflakes and flake8 versions"