This question clearly belongs on StackOverflow, but the poster has stated they were banned in the comments, in response to stating the question belonged on SO. In my humble opinion, using another StackExchange site to circumvent a ban on another is unethical behaviour; I'm not sure how the community feels about it, but I can't imagine it's exactly smiled upon.
Should I flag the question? It's already on-hold, but I don't know if any moderators have noticed the person said that.
I agree with everything you said, but I'm not sure what you'd be flagging the post for or what action you expect to be taken at this point. We mostly don't care about a user's status on other SE sites; as long as the post is valid here we'll take it. On the other hand, as you said that post clearly belongs on SO since it requires knowledge of Python. Given that, it should be closed as off-topic no matter who asked it. If we try to migrate a post to a site where the asker is banned, it just gets converted to a normal off-topic closure, so there's no danger of them using us to backdoor a post onto a site they can't post on directly.
