Flask reloader crashes with "no module named Scripts\flask" on Windows

Question

When I run flask run on Windows, I get the following error

C:\Python37\python.exe: No module named C:\Python37\Scripts\flask

This was working previously, the issue started after I created a new env recently.

Answer 1

This was a bug introduced in Werkzeug 0.15.5. Upgrade to at least Werkzeug 0.15.6, which contains the fix. You can also run with python -m flask run instead to work around it.