When running python -S, attempting to run "import genericpath" fails with an attribute error due to a circular dependency between posixpath and genericpath that's triggered when "import os" is called from within genericpath.py. 

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/fbcode/platform007/lib/python3.7/genericpath.py", line 6, in <module>
    import os
  File "/usr/local/fbcode/platform007/lib/python3.7/os.py", line 57, in <module>
    import posixpath as path
  File "/usr/local/fbcode/platform007/lib/python3.7/posixpath.py", line 130, in <module>
    splitext.__doc__ = genericpath._splitext.__doc__
AttributeError: module 'genericpath' has no attribute '_splitext'

Thanks for the report, Brittany, but I'm closing as "won't fix" as the only way to make this happen is to import genericpath directly which one shouldn't do (it's undocumented on purpose); always get a hold of this module via 'os'.

See also issue31802. I skipped genericpath because I did not expect that somebody can import it directly (unlike to posixpath, ntpath and macpath). genericpath is an internal module, it is not even documented.