BUG: pytest --last-failed --last-failed-no-failures doesn't seem to work with tox

If I run the pytest locally, outside of tox, it works as expected and doesn't run the full suite on the second run if there were no failing tests. 

However, when reusing an existing tox environment (well, the point of tox really), then it runs the full suite -- I suspect it's a caching issue or an upstream one, if the latter I'll propagate it to the correct place.