It certainly wasn't clear to me that the variable assigned by
pytest.mark.usefixtures should also be called pytestmark,
so I was confused when::
foo = pytest.mark.usefixtures('fixture_bar')
wasn't behaving as expected; correct usage is of course::
pytestmark = pytest.mark.usefixtures('fixture_bar')
I assume this is by design, otherwise that's a separate issue, at
least current behaviour should be documented.