Run pycodestyle on your file and display the results nicely. Based on Pierre Pracht's Python PEP8.tmbundle.
cd ~/Library/Application\ Support/TextMate/Bundles/
git clone https://github.com/tungol/pycodestyle-tmbundle "pycodestyle.tmbundle"
You can set the executable of pycodestyle you'd like to use by editing the command and changing the PYCODESTLE variable.
After running the command, use controls in the upper-right to toggle display of code and PEP description. Hide specific errors by listing their code in the text field.