How do I enforce unique user names in Flask?
You can use SQLAlchemy.It's a plug-in
I'm a complete beginner to Flask and I'm starting to play around with making web apps. 
I have a hard figuring out how to enforce unique user names. I'm thinking about how to do this in SQL, maybe with something like user_name text unique on conflict fail, but then how to I catch the error back in Python?
Alternatively, is there a way to manage this that's built in to Flask?