Pytest "Error: could not load path/to/conftest.py" - pytest

Question

I get the following error when I try to run pytest repo/tests/test_file.py:
$ pytest repo/tests/test_file.py
Traceback (most recent call last):
File "/Users/marlo/anaconda3/envs/venv/lib/python3.6/site-packages/_pytest/config.py", line 329, in _getconftestmodules
return self._path2confmods[path]
KeyError: local('/Users/marlo/repo/tests/test_file.py')
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/Users/marlo/anaconda3/envs/venv/lib/python3.6/site-packages/_pytest/config.py", line 329, in _getconftestmodules
return self._path2confmods[path]
KeyError: local('/Users/marlo/repo/tests')
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/Users/marlo/anaconda3/envs/venv/lib/python3.6/site-packages/_pytest/config.py", line 362, in _importconftest
return self._conftestpath2mod[conftestpath]
KeyError: local('/Users/marlo/repo/conftest.py')
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/Users/marlo/anaconda3/envs/venv/lib/python3.6/site-packages/_pytest/config.py", line 368, in _importconftest
mod = conftestpath.pyimport()
File "/Users/marlo/anaconda3/envs/venv/lib/python3.6/site-packages/py/_path/local.py", line 686, in pyimport
raise self.ImportMismatchError(modname, modfile, self)
py._path.local.LocalPath.ImportMismatchError: ('conftest', '/home/venvuser/venv/conftest.py', local('/Users/marlo/repo/conftest.py'))
ERROR: could not load /Users/marlo/repo/conftest.py
My repo structure is
lib/
-tests/
-test_file.py
app/
-test_settings.py
pytest.ini
conftest.py
...
Other people have run this code fine, and according to this question (and this one), my structure is good and I am not missing any files. I can only conclude that something about my computer or project set-up is not right. If you have any suggestions or insights that I may be missing, please send them my way!
-------------------------------MORE DETAILS------------------------------
test_file.py:
def func(x):
return x + 1
def test_answer():
assert func(3) == 5
pytest.ini:
[pytest]
DJANGO_SETTINGS_MODULE = app.test_settings
python_files = tests.py test_* *_tests.py *test.py

Answer 1

I have docker as well as running pytest outside of docker too, and for me a much lower-impact fix whenever this crops up is to delete all the compiled python files
find . -name \*.pyc -delete

Answer 2

I figured it out and I'll answer in case others have the same issue:
I didn't even take into consideration that I had a docker container (of the same app) in the repo directory and, although I was not running the docker container, it was influencing the filepaths somehow.
To fix this:
I re-cloned the repo from the remote source into a new folder so that nothing from the old repo could "contaminate" it.
Updated my virtual environment with the .yml specifications of the clean repo
$ conda env update --name project --file project.yml
My project uses a postgres database, so I dropped it and created a new one
$ dropdb projectdb
$ createdb projectdb
Since my project uses mongo, I also dropped that database
$ mongo projectdb --eval "db.dropDatabase()"
Installed a clean pytest
$ pip uninstall pytest
$ pip install pytest
...and voilà! I could run pytest.
Many thanks to #hoefling and others who helped me debug.

Answer 3

I was running docker as well, but it seems my problem was different.
I was using an old version of pytest:
platform linux -- Python 3.9.7, pytest-3.7.2, py-1.10.0, pluggy-1.0.0
which stopped working after my ubuntu image was pulling python 3.10 by default.
my solution was to update (and fix) the dockerfile image to use:
FROM python:3.10
instead of python:latest, and update the pytest version as well.