Converting a driver to pass tests on python3 is not quite the same
as it actually working in the real world. We need to keep track of
which drivers have been tested in the wild, separate from those that
merely pass tests.
This adds a file tests/py3_driver-testers.txt, which is a simple list
of the driver ID key and the person/date when it was tested. Running
the "makesupported" tox target will also generate
tests/Python3_Driver_Testing.md, which will be render-able in github
for easy viewing.
If you test a driver on python3, please add a line to the tracking
file, run the makesupported target, and update the markdown file.