[MRG] update to Python>=3.8

[rythorpe]

The latest releases of Matplotlib now require Python>=3.8. This updates our tests and installers correspondingly.

[rythorpe]

Okay, I'm pretty sure everything should pass now. Feel free to squash and merge if/when it does @ntolley @jasmainak so we can build and update our docs on master.

[codecov-commenter]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (91b8ff6) 91.42% compared to head (4d5ccf4) 91.38%.

❗ Current head 4d5ccf4 differs from pull request most recent head 9205e61. Consider uploading reports for the commit 9205e61 to get more accurate results

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #678      +/-   ##
==========================================
- Coverage   91.42%   91.38%   -0.04%     
==========================================
  Files          25       25              
  Lines        4604     4599       -5     
==========================================
- Hits         4209     4203       -6     
- Misses        395      396       +1     

see 3 files with indirect coverage changes

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[rythorpe]

Note that this was changed because the mpi4py installation was failing for Ubuntu/Python 3.9. Not totally sure what the root of the issue was.

[ntolley]

Assuming the default repository identified for the conda install had an old/incompatible version?

[rythorpe]

Something like that. We technically shouldn't need to install the openmpi python library on Linux if it's already installed at the system level, but now we can just rely on wheels that are compiled and tested by the maintainers of mpi4py.

[jasmainak]

I enabled auto-merge. Thanks a lot @rythorpe !! 🎉

[rythorpe]

How do we change the merge requirements @jasmainak? Right now you're the only one who can approve merges or enable auto-merges.

[jasmainak]

Umm ... I think anyone with merge rights can enable auto-merges ... but if the CIs are not passing, you have to select "Merge without waiting for requirements to be met". I would select this sparingly though ...

[jasmainak]

The macos build seems to be stuck for whatever reason ...

[rythorpe]

Did you disable auto-merge on purpose @jasmainak, or did it cancel when you modified the branch protection rules?

[rythorpe]

I'm guessing it just cancelled on its own so I went ahead and merged it 🚀

[jasmainak]

Thanks @rythorpe !