Python versions I have to target (occasionally): 2.5, 2.7, 3.5, 3.8. Not the whole world has the luxury to upgrade all their systems all the time. Excuse me,

Python versions I have to target (occasionally): 2.5, 2.7, 3.5, 3.8. Not the whole world has the luxury to upgrade all their systems all the time. Excuse me, would you mind stopping this factory for a few hours so we can replace this perfectly functioning system with an untested one that may or may not work in roughly the same way? is not a question that is generally met with wild enthusiasm.