CI Upload to pypi with GitHub actions

[thomasjpfan]

Moved here from MacPython/scikit-learn-wheels#65

This PR adds a github action so we can upload with pypi through the interface.

1. One needs to add the PYPI_TOKEN secret to enable uploading to pypi. (I already added a TEST_PYPI_TOKEN for testpypi).
2. One has to type in pypi in the "Run workflow" UI to upload to pypi, otherwise it will upload to testpypi by default.
3. There is a check_artifacts.py script that makes sure that wheelhouse_uploader fetches the correctly number of artifacts based on the azure-pipeline.yml configuration.

[rth]

Generally LGTM, but maybe @alfaro96 could have a look as well.

[alfaro96]

Thank you @thomasjpfan for your PR!

LGTM too.

Do you mind updating the doc/developers/maintainer.rst file to refer to the new PyPI uploading system?

[ogrisel]

Let me do the following change:

[ogrisel]

@thomasjpfan out of curiosity how do you test github actions? I have a dedicated github fork of the scikit-learn repo where you forcepush your branch to the remote master?

[thomasjpfan]

@thomasjpfan out of curiosity how do you test github actions? I have a dedicated github fork of the scikit-learn repo where you forcepush your branch to the remote master?

For most GitHub Actions, they are triggered when I push a branch to my fork.

The complicated one is the pull_request_target trigger, where I want the workflow to have access to secrets, but triggered by a pull request. For testing this, I would force push to master and open a pull request to the fork.

[ogrisel]

LGTM, let's merge.

I tested it (without the secrets) on my fork. I will add the token for the pypi.org site once merge so that we can give it a try for the upcoming 0.24 release candidate.

[ogrisel]

Do you mind updating the doc/developers/maintainer.rst file to refer to the new PyPI uploading system?

Forgot about this step will do a PR.