CI flake: pip update may not do anything

[henryiii]

Probably should add a test forcing the exact minimum supported pip. The pip changelog is terrible about not having the details of when things get added or removed (try to find when eggs were dropped, for example).

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I believe this requires Pip 19.something (0 or 1), we need to bump the minimum check. It’s currently breaking our CI (macOS Python 3.6 has 18.something which is missing this flag).

Originally posted by @henryiii in #232 (comment)

[layday]

I thought we already require 19.1 as a minimum. Do you have a link to the CI output?

[henryiii]

That’s weird, we do. At least we try to. It’s the most recent build.

https://github.com/pypa/build/runs/2068846663?check_suite_focus=true

Requirement already up-to-date: pip in /private/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/build-env-zd7okh36/lib/python3.6/site-packages (18.1)
Uninstalling setuptools-40.6.2:
  Successfully uninstalled setuptools-40.6.2

[henryiii]

Note that is trying to update, I think, but printing out that it is already up to date at version 18.1. (On a phone, so a little hard to debug). Would requiring a modern version in the update command help (would it ever not update without it?)? If we manually update, we should be at 20.3.4+.

[layday]

This is probably a flake or it would've popped up in CI before today.

[gaborbernat]

Note we can use virtualenv to create an environment with the exact pip version and run the test it those.

[henryiii]

Pretty sure the issue is that when PyPI can't be reached, "upgrade" simply does nothing.