`pytest --rm success ...` not working as intended

Summary

gmxapi.testsupport adds support for a --rm option to pytest. The value of success is supposed to remove the testing temporary directory only when a test succeeds. At some point the logic seems to have broken, and the temporary directory is always removed unless --rm never.

GROMACS version

2020 and newer, but possibly dependent on pytest version.

Steps to reproduce

1. Install gmxapi, or build GROMACS with -DGMX_PYTHON_PACKAGE=ON and change to the ${CMAKE_BUILD_DIR}/python_packaging/src/gmxapi_staging directory.
2. python -m pytest <other pytest args> --rm success /path/to/python_packaging/src/test/<failing_test>

What is the current bug behavior?

pytest --rm never works as expected, but --rm success proceeds as if --rm always

What did you expect the correct behavior to be?

As with --rm never, the temporary directory for a failed test should not be removed. Unless suppressed, a warning like the following would be visible:

===================================================================================== warnings summary ======================================================================================
test_subgraph.py::test_subgraph_simulation_extension
  .../python_packaging/src/gmxapi_staging/gmxapi/testsupport.py:194: UserWarning: Temporary directory not removed: /<tmp_dir_path_prefix>/tmp6e9mml_d

Possible fixes

pytest provides tmp_path and tmp_path_factory fixtures that do most of what we need, but which have a different retention policy that avoids some of the other issues we've run into. We can build on these fixtures, instead.

Issues avoided:

• race conditions in directory removal
• custom policies on temporary directory retention
• extra custom command line argument processing
• appropriate reporting of the temporary directory path and status