pytest /dev/null crashes

[asottile]

to be fair, this might not be worth fixing -- though I was surprised to see this output:

$ pytest /dev/null
============================= test session starts ==============================
platform linux -- Python 3.6.6, pytest-4.0.1.dev42+g23e44479, py-1.7.1.dev3+gb9da2ed6, pluggy-0.8.0
rootdir: /dev, inifile:
collected 0 items / 1 errors                                                   

==================================== ERRORS ====================================
______________________________ ERROR collecting  _______________________________
venv/lib/python3.6/site-packages/_pytest/runner.py:211: in __init__
    self.result = func()
venv/lib/python3.6/site-packages/_pytest/runner.py:272: in <lambda>
    call = CallInfo(lambda: list(collector.collect()), "collect")
venv/lib/python3.6/site-packages/_pytest/main.py:495: in collect
    for x in self._collect(arg):
venv/lib/python3.6/site-packages/_pytest/main.py:571: in _collect
    assert argpath.check(file=1)
E   AssertionError
=============================== warnings summary ===============================
venv/lib/python3.6/site-packages/_pytest/cacheprovider.py:119
  /home/asottile/workspace/pygments-pytest/venv/lib/python3.6/site-packages/_pytest/cacheprovider.py:119: PytestWarning: could not create cache path /dev/.pytest_cache/v/cache/stepwise
    self.warn("could not create cache path {path}", path=path)
  /home/asottile/workspace/pygments-pytest/venv/lib/python3.6/site-packages/_pytest/cacheprovider.py:119: PytestWarning: could not create cache path /dev/.pytest_cache/v/cache/nodeids
    self.warn("could not create cache path {path}", path=path)
  /home/asottile/workspace/pygments-pytest/venv/lib/python3.6/site-packages/_pytest/cacheprovider.py:119: PytestWarning: could not create cache path /dev/.pytest_cache/v/cache/lastfailed
    self.warn("could not create cache path {path}", path=path)

-- Docs: https://docs.pytest.org/en/latest/warnings.html
!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!!
===================== 3 warnings, 1 error in 0.15 seconds ======================

[asottile]

I guess this wouldn't work anyway since pytest assumes a file ends with .py or it is a directory containing tests

[blueyed]

I think this is a good corner case, i.e. it is worth fixing.

Might be just that the assertion there should be removed/changed.

[asottile]

touch t
pytest ./t

Also doesn't work so I expect this to be difficult