gh-133307: Add new Pdb config location $XDG_CONFIG_HOME/pdb/.pdbrc

[makukha]

• Issue: Respect $XDG_CONFIG_HOME/pdb/.pdbrc path for PDB config discovery #133307

---

📚 Documentation preview 📚: https://cpython-previews--133733.org.readthedocs.build/

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

[gaogaotiantian]

I'm a -1 on this one. We don't have anything in CPython that's using $XDG_CONFIG_HOME for now. We do have a few cases where we read config files from home dir like IDLE or netrc. This increases the maintenance effort, introduces some inconsistency, without much benefits. I understand that this method stores the user data/config per app instead of per user, but if we really need to do that, we should do it for the whole Python, not just pdb - then it would probably be a PEP-level change.

I think you need to at least get some supports from other people - users from d.p.o. and/or some core devs. That would show that people are interested in this feataure. At this moment I'm not fully convinced that we should have this.

[makukha]

@gaogaotiantian thank you for the detailed response! Could you please keep this PR open for a week or two? I'll drop a post in Discourse and get back here.

[gaogaotiantian]

I won't close this PR. Feel free to gather some opinions and promote this again in the future.