Multi Platform CI Pipeline with GitHub Actions

[callmecampos]

Per discussion in #650, this PR leverages GitHub Actions to test twine against Ubuntu, macOS, and Windows.

This involved some changes to the twine.wheel unit tests, specifically surrounding the assumption of Unix/Posix environments for path representations. To fix this, we now use pathlib in the wheel unit tests to represent paths, since when initializing a pathlib.Path object, pathlib automatically returns a PosixPath or a WindowsPath dependent on the operating system at runtime.

Additionally, integration tests test_devpi_upload and test_pypi_server_upload are expected to fail on Windows and thus skipped since they're using pytest-services' watcher-getter fixture, which doesn't support Windows according to pytestservices:#22.

There has also been discussion in #650 about replacing Travis entirely with GitHub Actions, which is reasonable enough, though .travis.yml also includes a code coverage step (codecov --env TRAVIS_OS_NAME, TOX_ENV) which I don't believe we currently have with GitHub Actions. Talking with @di, we could move to using a different coverage tool like https://pypi.org/project/coverage/. This can be done in this PR or a later one which migrates away from Travis completely towards GitHub Actions.

Update 6/5/20: Added code coverage to the config file.

[di]

Also, since @callmecampos is not a maintainer, the action won't run on this PR, but you can see it running on his branch here: https://github.com/callmecampos/twine/actions?query=branch%3Amulti-platform-ci

[sigmavirus24]

What would the steps be after merging this, @di?

[di]

Aside from removing the Travis config in a separate PR, nothing. Once merged it will run on all PRs and pushes.

[sigmavirus24]

@callmecampos can you resolve the merge conflicts here?

[callmecampos]

@sigmavirus24 merge conflicts resolved and new CI checks passed here: https://github.com/callmecampos/twine/actions/runs/127062822

[bhrutledge]

Apologies for the late review here. I noticed a few things, but they don't need to hold up a merge; happy to address them later.

[callmecampos]

@bhrutledge I made the changes you suggested, thanks for reviewing!

Also, according to codecov/codecov-action#37 there have been issues with codecov uploads timing out with GitHub Actions, so instead of uploading Coverage.py's XML report using python -m coverage xml, I'm just running python -m coverage report which directly prints out the report per @di's suggestion. See https://github.com/callmecampos/twine/actions/runs/128994913 for the most recent passing GitHub Actions checks.

[bhrutledge]

Thanks! One small change to avoid redundancy.

That's a bummer re: Codecov. I opened #658 to consider replacing it.

Also, looking at the commit history, I think this should be squashed, either using the "Squash & Merge" button when it's ready, or locally via git rebase -i.

[bhrutledge]

Following up on this:

there have been issues with codecov uploads timing out with GitHub Actions

@callmecampos, have you seen timeouts in practice? From a GitHub search, it looks this action is widely used, including by some high-profile Python projects:

• https://github.com/python-attrs/attrs/blob/master/.github/workflows/main.yml
• https://github.com/pypa/virtualenv/blob/master/.github/workflows/check.yml
• https://github.com/Python-Markdown/markdown/blob/master/.github/workflows/tox.yml
• https://github.com/dateutil/dateutil/blob/master/.github/workflows/test_pypy.yml
• https://github.com/jazzband/pip-tools/blob/master/.github/workflows/ci.yml

With that list, I guess I'd be surprised if it's not safe to use.

[callmecampos]

@bhrutledge Yeah, I was seeing it sporadically yesterday. If you go to this run here, and click on the failing job (Upload coverage to Codecov) you'll see an example of it failing because of timing out.

[bhrutledge]

@callmecampos Thanks for the link. Now that you mention it, I have seen those errors before; I usually just restart the job when that happens.

As long as we still have Travis, I think this Actions setup is great. When we drop Travis, we'll need to add types, docs, and release stages. It might also be worth revisiting Codecov.

[di]

I've added a checklist which includes all of those to #650.

[di]

You can now see the successful run here: https://github.com/pypa/twine/actions/runs/131530548