Hangs when running with gevent

[felixonmars]

To reproduce, create a conftest.py with the following content:

from gevent import monkey
monkey.patch_all()

And run py.test --flake8 in that folder.

py.test itself runs fine, so does flake8, but pytest-flake8 hangs.

[felixonmars]

After some investigation, this seems to be incompatibilities between gevent and multiprocessing that flake8 utilizes.

Adding a app.file_checker_manager.using_multiprocessing = False right after app.make_file_checker_manager() in pytest_flake8 fixes this for me.