[3.13] gh-82916: Don't fail when importing from / with sys.pycache_prefix set (GH-30456)

[miss-islington]

(cherry picked from commit d8a9466)

Co-authored-by: Petr Viktorin encukou@gmail.com
Co-authored-by: Serhiy Storchaka storchaka@gmail.com

• Issue: PYTHONPYCACHEPREFIX fails when importing a module from the root ("/") #82916

[encukou]

This should be merged after #137906 (3.14.1).

[Yhg1s]

This should be merged after #137906 (3.14.1).
Why shouldn't this go into 3.13.8 (which is scheduled for around the same time as 3.14.0)?

[encukou]

Well, I'll generally backport in order. Do you want it in 3.13.8 but not 3.14.0?

[Yhg1s]

Well, I'll generally backport in order. Do you want it in 3.13.8 but not 3.14.0?

Is there a reason not to have it in 3.13.8? :) I'm not sure why we wouldn't distribute the fix in 3.13 just because 3.14 has its own stabilization phase before the final release. I think I've done similar in 3.12 while 3.13.0 was in RC phase.

[Yhg1s]

FWIW I double-checked with @hugovk (and also @gpshead chimed in) and the fact that it isn't in 3.14 yet is fine, it should still be fixed in 3.13 (and this isn't the only bugfix that would be in 3.13 but not 3.14, we have lots of other fixes pending in 3.14.)

[encukou]

Alright, I'll do that from now on :)