add newer Python versions in OSX to Github Actions

[bvreede]

To make sure that recently fixed tests (and other issues) are run on OSX as well as Linux, newer versions of Python (3.8 and 3.9) are added to Github Actions.

Follows up on #1003

NB: the Anaconda Publish action fails, which it does on Master too, e.g. @ESMValGroup/esmvaltool-coreteam

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Before you get started

• ☝ Create an issue to discuss what you are going to do

Checklist

• PR has a descriptive title for the changelog
• Labels are assigned so they can be used in the changelog
• Code follows the style guide
• Documentation is available for new functionality
• YAML files pass pre-commit or yamllint checks
• Circle/CI tests pass
• Codacy code quality checks pass
• Documentation builds successfully on readthedocs
• Unit tests are available

If you make backwards incompatible changes to the recipe format:

• Update ESMValTool and link the pull request(s) in the description

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To help with the number pull requests:

• 🙏 We kindly ask you to review two other open pull requests in this repository

[bouweandela]

NB: the Anaconda Publish action fails, which it does on Master too, e.g. @ESMValGroup/esmvaltool-coreteam

Reported it in #1036

[valeriupredoi]

nice work @bvreede - could you please first test all the additional actions (for 3.9) in a test branch - like the ga_test one you've already added, then post the pass/fails here, and if all passes fine, remove that test branch from the triggers' list and then I will approve and it'll be ready to go. Sorry, am requesting changes now only for this technicality, the changes look perfect! 🍺

[bvreede]

Thanks very much @valeriupredoi! We did that already, if I understand you correctly. I just added the current branch as a trigger in the relevant actions, is that what you mean? In any case, the actions were run on this branch (though I see now that the last time this was done, the tests failed on Python OSX 3.7 — not one we added, and tests have been off and on failing on random systems, it must be the weather. Still, will double check).

I removed it in all but one (relevant) action here.

All actions passed, except Anaconda Publish, as mentioned. I'm waiting for that one to function again on master before I confirm that this branch does not add failures (hence the draft status of this PR ;))

[valeriupredoi]

cheers @bvreede - good stuff! You can filter the actions on branch name - here the results filtered only on ga_osx https://github.com/ESMValGroup/ESMValCore/actions?query=branch%3Aga_osx (verbose link) which I should have looked at myself before asking you to instate such a test branch. Cool! They run fine - bar the segfault which is common and the circular import issue preventing conda build tests to pass (which I fixed in the other PR). Now, could you pls remove the ga_osx from the workflow files and after that we're good to go! Cheers 🍺

[bvreede]

OK done — perhaps best to merge this now & I'll keep a close eye on the Anaconda Publish action.

[valeriupredoi]

excellent work @bvreede cheers muchly! 🍺