One issue with this is that I believe it will catch 500 errors returned by the API so :(

It actually won't, because API errors are already caught by @api_method: https://pagure.io/pagure/blob/master/f/pagure/api/init.py#_231

That endpoint catches the exception raised in the API returns the error code (including possibly a 500) which will then the generic flask handler catches

As to why this doesn't hit in our deployments, the code that checks this is:

            assert code_or_exception != 500 or key is None, \
                'It is currently not possible to register a 500 internal ' \
                'server error on a per-blueprint level.'

Any assert statements get stripped with optimized python, which happens in the Fedora pacakges.

Ok despite what I thought it seems to not catch 500 from the API, so let's rebase and merge :)