The current version of pyflakes (2.2.0) correctly detects one issue:
mercurial/thirdparty/selectors2.py:335:40 '...'.format(...) has unused arguments at position(s): 1
But we're not interested in fixing lint errors in third-party code, so we need
to exclude at least selectors2.py. And in the discussion for this patch it was
decided to just skip the entire thirdparty directory.
Wouldn’t it make sense to skip everything in mercurial/thirdparty?