pytest's assertion rewriting causes pytest-xdist to not being uninstalled completely

[blueyed]

pip uninstall pytest-xdist leaves files behind when pytest has created files via its assertion rewriting:

./.venv/lib/python3.7/site-packages/xdist
├── __pycache__
│   ├── dsession.cpython-37-PYTEST.pyc
│   ├── looponfail.cpython-37-PYTEST.pyc
│   ├── newhooks.cpython-37-PYTEST.pyc
│   ├── plugin.cpython-37-PYTEST.pyc
│   ├── remote.cpython-37-PYTEST.pyc
│   ├── report.cpython-37-PYTEST.pyc
│   ├── _version.cpython-37-PYTEST.pyc
│   └── workermanage.cpython-37-PYTEST.pyc
└── scheduler
    └── __pycache__
        ├── each.cpython-37-PYTEST.pyc
        ├── load.cpython-37-PYTEST.pyc
        ├── loadfile.cpython-37-PYTEST.pyc
        └── loadscope.cpython-37-PYTEST.pyc

3 directories, 12 files

pip 18.1 (python 3.7.2)

I've noticed this, because pytest.importorskip will not skip it then.

[nicoddemus]

Weird, at first glance I don't think this is anything related to xdist in particular, but for every pytest plugin. 🤔

[blueyed]

Yeah, likely.

[asottile]

maybe we should take #4730 and default to .pytest_cache/pycache (even on older python versions) -- since pytest controls the pyc loading anyway there's nothing binding us to the source directories

[blueyed]

@asottile
Sounds like a good plan.