GitHub Action: Run Python tests on Ubuntu & macOS

[cclauss]

Running Python standalone tests on multiple OSes would free up Travis CI for tests of various combinations of Node.js and Python as well as tests on other CPU architectures.
arch: amd64, arm64, ppc64le, s390x

Checklist

• npm install && npm test passes
• tests are included
• documentation is changed or added
• commit message follows commit guidelines

Description of change

[rvagg]

I'd love if we could push as much as possible to GitHub Actions with a view to one day retiring Travis. What exactly can't we do on Actions yet? Is it just the non-x64 architectures? When they launch self-hosted runners we could start using Node infra to do these ourselves. Not sure what the timeline is on that though.

[cclauss]

using-self-hosted-runners-in-a-workflow

[rvagg]

nice!

sadly they're still being restrictive on OS/arch support: https://help.github.com/en/actions/automating-your-workflow-with-github-actions/about-self-hosted-runners#supported-operating-systems-for-self-hosted-runners

but they did talk about making this supported on more permutations and I bet IBM are already talking to them about adding their platforms.

[cclauss]

Can I please get you review on this in its current state? I would be interested to land is so we can start exploring the three todos.

[rvagg]

5a64e9b