[Answered ]-Django – value too long for type character varying (but appears to be within max_length limit)

So when doing:

self.question.some_property = form.cleaned_data['some_property'],

I appended a trailing comma by accident, and that didn’t raise a syntax error for my particular code somehow, but went right through psycopg2 to the database as a dodgy query. That’s probably a really obscure error that won’t happen to anyone else, but I’ll leave the question up in case the debugging procedure is useful for folks.