Running "tox -e integration" takes a while. It would be helpful to
run tests from just one file. With this change, we can do that, like
so:
$ tox -e integration -- integration/test_web.py
Or even just one test, like so:
$ tox -e integration -- integration/test_web.py::test_index
With this investigating failing integration tests will be a little
easier, hopefully.
Fixes: ticket:3285
