The fact that they couldn't find it by looking at error logs is weird to me.

This is an entirely forgivable error but should have been found the first time they got an email about it:

"Oh, look, the error logs have a duplicate key exception for the primary key, how do we generate primary keys.... (facepalm)"

Funnily enough, I saw the error in their snippet as soon as I read it but dismissed it thinking there was some new-fangled python feature which allowed that to work like the function def defines that default= accepts only functions so the function gets passed? -- I haven't kept up with modern python and that sounds cool and I figured the bug couldn't be THAT simple.