Make winreg import compatible to modern Python

[uranusjr]

Fix #7495.

I intend to work on #6040 to eliminate the internal copy next, but figured it’s better to post this quick fix first.

[xavfernandez]

A bugfix newsfile is needed and ideally a test also :)

[uranusjr]

I am without a computer so the news is the best I can do now :(

[chrahunt]

This is pretty much verbatim what is in the upstream version (except PY2 vs PY3), and we're trying to get rid of the bundled version anyway, so I'm personally OK with no tests in this case.

[uranusjr]

I thought about it a bit but am not sure how to meaningfully test this :/

[xavfernandez]

I thought about it a bit but am not sure how to meaningfully test this :/

Simply calling site_config_dirs() with PY2/3 & with/without ctypes ?

[uranusjr]

with/without ctypes

Is there a way to make import ctypes unavailable in the test? (without e.g. deleting the module from stdlib)

[xavfernandez]

@uranusjr cf

pip/tests/unit/test_utils.py

Line 599 in 2472a6e

monkeypatch.setitem(sys.modules, "ctypes", None)

for an example

[xavfernandez]

I was actually hoping that winreg.OpenKey and winreg.QueryValueEx could be called for real on Windows. Is there a blocker ?

[uranusjr]

Not blocker but I don’t think it’s meaningful. Their return values might not be predictable (being essentially system configuration).

[uranusjr]

Closing since #7501 is now in a mergeable state