I would like to do error handling conditionally, like:

def internal_error(exc: peewee.InternalError) -> Optional[Response]:
    if exc.args[0] == 1213:
        # Deadlock found when trying to get lock; try restarting transaction
        return CustomErrorResponse(...)

def any_exception(exc: Exception) -> Response:
        return CustomErrorResponse(...)

app.register_error_handler(peewee.InternalError, internal_error)
app.register_error_handler(Exception, any_exception)

Could it be so that if None is returned from an errorhandler, Flask keeps on iterating and calls the next suitable errorhandler?

Lines: https://github.com/pallets/flask/blob/master/flask/app.py#L1521-L1525 Looks like the code has changed somewhat since 0.10.1 that I'm running (in 0.10.1 this would have been 3-line change I think).

Of course I could call return any_exception(exc) from internal_error() but that kinda adds direct dependency between the two methods and I would like to avoid it (consider the error handlers coming from different modules/classes etc. and maybe there's even third error handler sitting between that would be skipped here).