Update Python to 3.9
Python 3.9 was released on Oct 5. There's nothing too significant in it, but a few minor things that will be nice to be able to use (for example, being able to use the built-in collection types in type annotations): https://docs.python.org/release/3.9.0/whatsnew/3.9.html#new-features
However, similar to when we updated to 3.8, pygit2 is currently unable to build under 3.9. There's an issue on their repo here: https://github.com/libgit2/pygit2/issues/1038
Edited by Deimos