cache: last_failed_paths might crash with ELOOP / does not honor/use args

[blueyed]

% COLUMNS=80 p --lf testing
============================= test session starts ==============================
platform linux -- Python 3.7.3, pytest-4.6.1.dev186+gc9923a3a5, py-1.8.0, pluggy-0.12.0
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase('…/Vcs/pytest/.hypothesis/examples')
rootdir: …/Vcs/pytest, inifile: tox.ini, testpaths: testing
plugins: hypothesis-4.23.8
collected 0 items / 1 errors
run-last-failure: 335 known failures not in selected tests

==================================== ERRORS ====================================
________________________ ERROR collecting test session _________________________
src/_pytest/cacheprovider.py:161: in last_failed_paths
    return self._last_failed_paths
E   AttributeError: 'LFPlugin' object has no attribute '_last_failed_paths'

During handling of the above exception, another exception occurred:
.venv/lib/python3.7/site-packages/pluggy/hooks.py:291: in __call__
    return self._hookexec(self, self.get_hookimpls(), kwargs)
.venv/lib/python3.7/site-packages/pluggy/manager.py:87: in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
.venv/lib/python3.7/site-packages/pluggy/manager.py:81: in <lambda>
    firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
src/_pytest/cacheprovider.py:175: in pytest_ignore_collect
    last_failed_paths = self.last_failed_paths()
src/_pytest/cacheprovider.py:165: in last_failed_paths
    result = {x for x in result if x.exists()}
src/_pytest/cacheprovider.py:165: in <setcomp>
    result = {x for x in result if x.exists()}
/usr/lib/python3.7/pathlib.py:1339: in exists
    self.stat()
/usr/lib/python3.7/pathlib.py:1161: in stat
    return self._accessor.stat(self)
E   OSError: [Errno 40] Too many levels of symbolic links: '…/Vcs/pytest/issue-4782/pkg/test_symlink.py'
=========================== short test summary info ============================
FAILED  - OSError: [Errno 40] Too many levels of symbolic links: '/home/danie...
!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!!
=========================== 1 error in 0.15 seconds ============================

I see two issues here:

1. it should not crash, but ignore the ELOOP - likely more a Python issue itself though
2. it should only consider files that would be collected anyway (i.e. using testpaths, or the arg in this case): then it would not look at that looping symlink in the first place.