AtlasPyFwdBwdPorts: fix pytest related build problems (ATLINFR-4022)
Remove the pytest
requirement from mccabe
and flake8
which all of
a sudden started to create problems. Since we only build these packages
and never run their tests this dependency is not really needed. It was
also removed upstream, see e.g. https://github.com/PyCQA/mccabe/pull/75.
Manual sweep of !41744 (merged).