Error running pycodestyle when pycodestyle is not installed

[nils-werner]

Whenever I start Atom in a virtualenv that doesn't have pycodestyle installed, I repeatedly get this error message, which makes working very very hard.

I get that not having pycodestyle installed is an error that should/could be messaged to the user, but currently it is showing me the error message every time I edit a file, which is incredibly annoying.

I would suggest removing the error message, or showing it only once.