This fixes running `pytest tests/test_foo.py::test_bar`, where `tests`
is a symlink to `project/app/tests`: previously
`project/app/conftest.py` would be ignored for fixtures then.
The problem was that _matchnodes would receive two items: [DoctestModule, Module]. It would then collect the first one, *cache it*, and fail to match against the name in the command line. Next, it would reuse the cached item (DoctestModule) instead of collecting the Module which would eventually find the "test" name on it.
Added the type of the node to the cache key to avoid this problem, although I'm not a big fan of caches that have different key types.
Fix#3843
Daniel Hahler
Ronny Pfannschmidt
Bruno Oliveira
Fabio Zadrozny
turturica
Anthony Sottile