Some time ago, we've unified our efforts to build & maintain code quality checkers. For instance, Flake8 is now entirely based on plugins: there's a pep8, pyflakes & mccabe plugin and you can add more.
The family of Flake8 plugin is growing & Florent has started listing them at http://flake8.readthedocs.org/en/latest/extensions.html#existing-extensions
Another good news is the creation of a mailing list dedicated to all the code quality tools : http://mail.python.org/mailman/listinfo/code-quality
If you're interested in those tools, or you are maintaing one yourself, consider joining this mailing list.