skip babel tests if locales aren't installed

[andrewgsavage]

• [ ] Closes # (insert issue number)
• [ ] Executed pre-commit run --all-files with no errors
• [ ] The change is fully covered by automated unit tests
• [ ] Documented in docs/ as appropriate
• [ ] Added an entry to the CHANGES file

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #2022 will not alter performance

_{Comparing andrewgsavage:convert (7576b2f) with andrewgsavage:convert (dd5e88f)}

Summary

✅ 437 untouched benchmarks