Pytest seems to be failing in certain environments

[glass-ships]

I've noticed some CI pipelines for test-backend passing, but locally as well as for other PR's (like #890 and #745) pytest is failing with something along the lines of:

ImportError: Error importing plugin "tests.fixtures.search_query": No module named 'tests'

Appears to be an issue with pytest trying to run/import conftest.py but I can't tell when this issue started or why it's complaining now (pytest version doesn't appear to have changed, and pinning to 8.2.0 doesn't fix the issue)

[kevinschaper]

I finally recognized this from when it started happening for me locally, I think it's when the PYTHONPATH isn't set to include the root of the python part of the project (./backend). Over in #937 I tweaked the action to include setting PYTHONPATH, and then changed the pytest commands to not look into backend/tests but just direct to tests (I'm a little confused by that, except that it must be a package argument rather than a path argument?).