Diagnostic error when processing package already installed with invalid requirement

[notatallshaw]

Fixes #12950
Fixes #12979

Creates a new exception message which gives the user a much clearer output:

$ python -m pip install --dry-run celery
Requirement already satisfied: celery in ./.venv/lib/python3.12/site-packages (4.4.7)
error: invalid-installed-package

× Cannot process installed package celery 4.4.7 in '/home/damian/opensource/contributions/pip/.venv/lib/python3.12/site-packages' because it has an invalid requirement:
│ Expected matching RIGHT_PARENTHESIS for LEFT_PARENTHESIS, after version specifier
│     pytz (>dev)
│          ~^
╰─> Starting with pip 24.1, packages with invalid requirements can not be processed.

hint: To proceed this package must be uninstalled using 'pip<24.1', some other Python package tool, or manually deleted.

Looking for feedback as I've never created a pip exception before and not sure how this would be tested.

[notatallshaw]

I've improved the message to make it a little bit more accurate (not always about uninstallation) and more actionable (gives the location it is installed).

Ready for review/merge.

[edmorley]

Thank you!

I like the revised wording of the error message (since the exception can occur even when not uninstalling).

[edmorley]

Could you update the PR description (and also the example in #12950 (comment)) to use the new wording (that's broader than just uninstall)?

[notatallshaw]

Could you update the PR description (and also the example in #12950 (comment)) to use the new wording (that's broader than just uninstall)?

Done

[edmorley]

Can this be merged? It would be great to get it into 24.3.

[notatallshaw]

One moment, I'm going to update this PR to also handle the exception in #12979, it's the same issue type (invalid installed package), but the exception is happening in a different location because it's slightly different (invalid version instead of invalid requirement).

[notatallshaw]

Done, now also fixes #12979, ready for re-review / merge (once #12964 lands anyway, which is currently blocking CI)