bpo-34977: Add Windows App Store package

[zooba]

Restores the original commit, plus the fix to ensure that when building on machines without recent MSVC/WinSDK we don't fail.

https://bugs.python.org/issue34977

[vstinner]

Please move the venv and tests change into a separated PR.

[bedevere-bot]

When you're done making the requested changes, leave the comment: I have made the requested changes; please review again.

[vstinner]

Please run a custom build on buildbot before merging this PR, I would prefer to not have to revert the change one more time :-)
https://bugs.python.org/issue34977#msg331322

[zooba]

How do you trigger a custom build these days? I couldn't find the UI.

[vstinner]

How do you trigger a custom build these days? I couldn't find the UI.

It's basically just a Git push to the right branch:

$ git push upstream <local_branch_name>:buildbot-custom

See https://devguide.python.org/buildbots/#custom-builders for more info.

Then you can go to https://buildbot.python.org/all/#/builders for example to see results: check the custom workers ran your job and check that they are green ;-) You should ignore unstable buildbots like Alpine or Clang UBSan custom. Well, we mostly care about Windows here :-)

[zooba]

I have made the requested changes; please review again

[bedevere-bot]

Thanks for making the requested changes!

@vstinner: please review the changes made to this pull request.

[pfmoore]

A couple of minor points, but generally this looks OK to me.

Outdated