Update Python and dependency versions for 5.0.x.
Review Request #12205 — Created March 23, 2022 and submitted
We're going to be dropping support for Python 2.x for the 5.0 release.
We already have made some changes to the code that affect this, but our
version specifiers and dependencies still had 2.x stuff in there. This
change updates everything so that we're Python 3.7+, and should make it
possible to run
setup.py --all-pyverssuccessfully again.
Ran setup.py and unit tests.