pytest-pep8 is broken

In !401 (closed) I have another pytest-pep8 problem. I get an errer while collecting test items and the error message is not helpful. Root of the problem seems to be that pytest-pep8 is not maintained anymore:

https://pypi.org/project/pytest-pep8/#history

A candidate for replacement seems to be flake8:

https://pypi.org/project/pytest-flake8/#history

Does one of you know anything about it? I will try to get it running and report back (or open a merge request).