title: pytest - run each test in a separate process
body: <p>I'm running a large suite of python tests using pytest, and some test results depend on the running order of the tests. For example if test B runs after test A then it can fail due to some initializations done in test A that affect test B.
  To circumvent this problem I would like to run each test in a new process, but the tests should still run sequentially and not in parallel.
  Is there a way to do that with pytest?</p>