Now each in-process pytest run saves a snapshot of important global Python
state and restores it after the test completes, including the list of loaded
modules & the Python path settings.
Previously only the loaded package data was getting restored, but that was
also reverting any loaded package changes done in the test triggering the
pytest runs, and not only those done by the pytest runs themselves.
Updated acceptance tests broken by this change, which were only passing before
by accident as they were making multiple pytest runs with later ones depending
on sys.path changes left behind by the initial one.
f3c9c6e8a8