Test/raises invalid regex errors

[hemanshu406]

Summary

• Added test coverage for invalid regular expression patterns passed to RaisesExc and RaisesGroup.
• Verified that malformed regex patterns raise the expected pytest validation errors.
• Improved edge-case test coverage without changing existing functionality.

Testing

• python -m pytest testing/python/raises_group.py -q
• 31 passed

Checklist

• Added relevant automated tests.
• Verified the relevant tests pass.
• Added a changelog fragment if required.
• Verified contributor information in AUTHORS.
• Verified AI assistance is credited in commit trailers.

AI Assistance

GitHub Copilot assisted with implementation and testing. The changes require human review and ownership before submission.