pytest-cov fails if we use os.chdir without changing it back to original working dir before tests finish running

[jcuna]

If you run tests on a script that performs os.chdir and does not return to original working dir, your pytest-cov will throw INTERNALERROR exceptions. A workaround is just to return to the original directory at the end of the script being tested.

I think that the pytest engine should itself save the initial working dir and return to it if it changed. I do not know yet if there're other side effects to this but if there are, then make the debug trace explain that the initial working dir changed since running the tests.

INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/_pytest/main.py", line 213, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/_pytest/main.py", line 257, in _main
INTERNALERROR>     config.hook.pytest_runtestloop(session=session)
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/pluggy/hooks.py", line 286, in __call__
INTERNALERROR>     return self._hookexec(self, self.get_hookimpls(), kwargs)
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/pluggy/manager.py", line 92, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook, methods, kwargs)
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/pluggy/manager.py", line 86, in <lambda>
INTERNALERROR>     firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/pluggy/callers.py", line 203, in _multicall
INTERNALERROR>     gen.send(outcome)
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/pytest_cov/plugin.py", line 254, in pytest_runtestloop
INTERNALERROR>     self.cov_controller.finish()
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/pytest_cov/engine.py", line 197, in finish
INTERNALERROR>     self.cov.stop()
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/coverage/control.py", line 675, in load
INTERNALERROR>     self._init()
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/coverage/control.py", line 223, in _init
INTERNALERROR>     set_relative_directory()
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/coverage/files.py", line 28, in set_relative_directory
INTERNALERROR>     RELATIVE_DIR = os.path.normcase(abs_file(os.curdir) + os.sep)
INTERNALERROR>   File "/usr/local/lib/python3.7/site-packages/coverage/files.py", line 163, in abs_file
INTERNALERROR>     path = os.path.realpath(path)
INTERNALERROR>   File "/usr/local/lib/python3.7/posixpath.py", line 396, in realpath
INTERNALERROR>     return abspath(path)
INTERNALERROR>   File "/usr/local/lib/python3.7/posixpath.py", line 383, in abspath
INTERNALERROR>     cwd = os.getcwd()
INTERNALERROR> FileNotFoundError: [Errno 2] No such file or directory

[nedbat]

This is a duplicate of #306.