Flask fails with “Error: While importing ‘X’, an ImportError was raised”, but does not display the error. How to find the source of the error?

Flask — 1 April 2023 · Comments off
Solution 1
$ python
>>> from my_app_folder import app

$ FLASK_APP='my_app_folder/app' FLASK_ENV=development flask run
Solution 2
    python wsgi.py

    flask run