#1131

Hi,
When running the tests after dropping 3.4, I also tested against 3.9 on Linux. All tests passed, so I was thinking to add simply add 3.9. But will probably want final 3.4 release cutting before either are merged?

Dropping 3.4 allows the use of function type hints and async/await coroutines.

Note: According to https://pypistats.org/packages/gitpython python 3.4 downloads are at 0.04% and 3.5 is still at 3.38%