[Python] ModuleNotFoundError: No module named 'passlib' despite passlib already being installed

I have a python module that tries to import from passlib.hash import pbkdf2_sha256, however when running the module, I get the ModuleNotFoundError.

I have tried running the module in my base environment, a venv, in a poetry shell, and I've tried reinstalling passlib through poetry install, pip install, pip install --force-reinstall, and none of it gets the module to see passlib being installed. I'm at a complete loss as to why this library just won't work.

The full error message is:

poetry run src/api-keychain/main.py --help
​

Traceback (most recent call last):
File "XXX/src/api-keychain/main.py", line 5, in <module>
from crypto import encrypt_key, decrypt_key
File "XXX/src/api-keychain/crypto.py", line 5, in <module>
from passlib.hash import pbkdf2_sha256
ModuleNotFoundError: No module named 'passlib'

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