3.10+ features to refactor: https://docs.python.org/3/whatsnew/3.10.html

Some issue to attack

• ignore_cleanup_errors=True not supported in Python 3.9 #2676
• Change all Optional[T] into T | None
• Change all Union[A, B, ...] into A | B | ...`
• Explore parenthesized context manager use
• Explore structural pattern-matching use