Fix #86

[jamesjuett]

This PR fixes #86.

Since Python 3.7, os.errno is no longer available.

[svenkreiss]

Thanks @jamesjuett . Do you have a reference for that?
It seems, in practice, os.errno still works because our tests are passing.

[jamesjuett]

Fair question! I've tracked down an authoritative source:

https://github.com/python/cpython/blob/main/Doc/whatsnew/3.7.rst#changes-in-the-python-api

(Near the bottom of the list, or just search for "errno".)

[svenkreiss]

Thanks for that reference. If you can fix the lint error (import order) then this is good to go.

[jamesjuett]

Ah yeah, my bad on the import ordering - fixed!

(Note on the force push...I'm on WSL and have issues with clock drift when my machine hibernates. The force push was after I realized my commit to fix the lint issue was showing up as several days ago.)

[svenkreiss]

Awesome. Thanks for the fix!