Fix xdg env in tests
This branch modifies setup.cfg and tox.ini so that the XDG_ family of environment variables are relocated into the temp directories used in tests, ensuring that host configuration cannot affect the tests in any way.
This branch modifies setup.cfg and tox.ini so that the XDG_ family of environment variables are relocated into the temp directories used in tests, ensuring that host configuration cannot affect the tests in any way.