Important Note: The issue has been fixed, but I am not hiding this project from the public as I used it as a reference in one of the Github issues. The problem occurred because Flask implicitly tries to use the load_dotenv() function when the python-dotenv package is installed in your virtual environment. This behavior conflicts when you try to load environment variables yourself, as I've done in src/settings.py. To solve this problem, you can set the load_dotenv argument to False when creating a Flask instance (see src/main.py for details).