[enekoreto]

Two strings still give SyntaxWarning: invalid escape sequence on Python 3.12+. The b_psycopg2.py one shows up in CI's test-persister-dbs job on main. Future Python versions plan to make it an error.

Changes

• b_psycopg2.py: the PostgreSQLPersister docstring has '\ ' in its docker example (line 41), so it's now a raw string.
• s3client.py: allowed_chars = r"a-zA-Z0-9_\-" in _allowed_project_name (line 101), the same fix b7547ed made in burr/tracking/client.py. The S3 client was added a few days before that and kept the old line.

How I tested this

• Compiled every .py file in the repo with warnings on: 2 SyntaxWarnings on main, none here.
• The docstring and allowed_chars are identical before and after, and _allowed_project_name gives the same result on main and here for a set of project names, with and without Windows.
• Full test suite and pre-commit pass, on Python 3.13 and 3.10.

Notes

Both strings keep exactly the same value, so the only change is the missing warning.

This was done with AI assistance (Claude Code), and checked by running the tests described above.

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.