Upgrade to Python 3.9

[nmck257]

Python 3.7 reached End of Life yesterday (June 27th, 2023): https://devguide.python.org/versions/

So, our priority order for upgrade recipes probably starts with 3.8, and then follows with 3.9, 3.10, 3.11, 3.12, etc.
Each upgrade recipe should chain to the previous upgrade recipe.

Scope:

• API/Feature Removals: https://docs.python.org/3/whatsnew/3.9.html#removed
• Behavior Changes: https://docs.python.org/3/whatsnew/3.9.html#porting-to-python-3-9
• (Maybe) Deprecations: https://docs.python.org/3/whatsnew/3.9.html#deprecated