Upgrade to 20.2 fails on Windows Server 2019

Environment

• pip version: 20.2
• Python version: 3.[6-8]
• OS: Windows Server 2019 via GitHubActions

Description

pip upgrade to 20.2 fails for Windows Server 2019. I’ve created a sample repository that runs pip install --upgrade with "pip==20.1.1" (old) and "pip==20.2" against all major platforms and Python 3.[6-8].

Note, that this is not a sudo issue, since the upgrade to the previous version runs fine.

Expected behavior

Upgrade without failures.

How to Reproduce

pip install --upgrade "pip==20.2"

Output

ERROR: Could not install packages due to an EnvironmentError: [WinError 5] Access is denied: 'C:\\Users\\RUNNER~1\\AppData\\Local\\Temp\\pip-uninstall-q3fbhmha\\pip.exe'
Consider using the `--user` option or check the permissions.

[uranusjr]

Yes, -m pip is the generally preferred way to run pip. There are even talks to deprecate the pip command entirely, but that’d be a very long term project.

[uranusjr]

Reading the implementation, the check (pip._internal.utils.misc.protect_pip_from_modification_on_windows) only guards against running through pip.exe (and the versioned variants), not pip without the extension. git blame led me to #7358, which removed the guard against the extension-less pip command since it mis-identifies python path\to\repo\src\pip as an error. The consensus seems to be that it is not worth the effort to improve the identification logic (my #7558 was closed unmerged), and pip should find a way to make this .exe replacement work, or deprecate the entry points altogether. So I’m closing this since the problem is tracked in #7567.