I was working on the really good (and free!) Real Python tutorial Python REST APIs With Flask, Connexion, and SQLAlchemy and came across the following error.
AttributeError: 'Marshmallow' object has no attribute 'SQLAlchemyAutoSchema'
It turns out that I needed to install not only marshmallow but also marshmallow-sqlalchemy. Run the following in your terminal/ shell.
python3 -m pip install marshmallow-sqlalchemy
Thanks to Art Chaz on Stack Overflow for the heads up.