Test Python 3.10 release candidate

[hugovk]

Python 3.10.0 final is due for release in October:

• https://www.python.org/dev/peps/pep-0619/

The first release candidate is now out and the Python release team has issued a call to action for community members:

We strongly encourage maintainers of third-party Python projects to prepare their projects for 3.10 compatibilities during this phase. As always, report any issues to the Python bug tracker.

https://discuss.python.org/t/python-3-10-0rc1-is-now-available/9982?u=hugovk

So let's also test 3.10 on the CI. The good news is everything passes.

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I didn't yet add 3.10 to the classifiers etc., that can wait until 3.10 is released and officially supported, but could be updated now if you wish.

I also added quotes around version numbers in YAML so it doesn't later interpret 3.10 as 3.1: https://dev.to/hugovk/the-python-3-1-problem-85g

[codecov]

Codecov Report

Merging #414 (8a121f9) into master (0b29b69) will increase coverage by 0.18%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #414      +/-   ##
==========================================
+ Coverage   76.20%   76.38%   +0.18%     
==========================================
  Files          14       14              
  Lines        1395     1406      +11     
==========================================
+ Hits         1063     1074      +11     
  Misses        332      332              

Impacted Files	Coverage Δ
src/wheel/macosx_libfile.py	94.47% <0.00%> (+0.39%)	⬆️

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[agronholm]

Thanks!

[agronholm]

One thing: how did you figure out 3.10-dev works? It's not mentioned anywhere on the list of supported Python releases, or any of the documentation of the setup-python action.

[hugovk]

x.y-dev has been used on Travis CI for a long time: https://docs.travis-ci.com/user/languages/python/#specifying-python-versions

And then I guess I found this issue to add the similar thing for GHA, which was added for 3.9-dev: actions/setup-python#20 (comment)

[agronholm]

Odd that they did not document this feature – an oversight on their part I suppose.

[fochoao]

Please watch my wheel package https://github.com/fochoao/wheel

[agronholm]

Please watch my wheel package https://github.com/fochoao/wheel

What for?

[fochoao]

[mattip]

Please stop spamming this repo.