flask_sqlalchemy: error with `__setattr__` to `DefaultMeta`

Question

After re-building a Docker image, I\'ve started to get the following error:

$ docker run --rm -it python:3.8-slim /bin/bash
...
$ pip install flask_sqlalchemy         


        

Answer 1

After some experimentation, it seems like the issue is due to some change between python:3.8.3-slim and python:3.8.4-slim.

To reproduce, notice that this works:

$ docker run --rm -it python:3.8.3-slim …

Where this does not:

docker run --rm -it python:3.8.4-slim …

It looks like this bug/fix is the cause of the issue: https://bugs.python.org/issue39960