Why don't I see errors from readline.set_completion_display_matches_hook?

Consider this code:

#!/usr/bin/env python3

from cmd import Cmd
import readline

class mycmd(Cmd):
    def match_display_hook(self, substitution, matches, longest_match_length):
        someNonexistentMethod()
        print()
        for match in matches:
            print(match)
        print(self.prompt, readline.get_line_buffer(), sep='', end='', flush=True)

    def do_crash(self, s):
        someNonexistentMethod()

    def do_quit(self, s):
        return True

if __name__ == '__main__':
    obj = mycmd()
    readline.set_completion_display_matches_hook(obj.match_display_hook)
    obj.cmdloop()

I expect to see NameError: name 'someNonexistentMethod' is not defined when I run that and hit TabTab. However, nothing actually seems to happen at all (the error does occur, so the other functions that would print the completion don't run; I just don't see the error). I do see the expected error when I run crash, so I know error handling works fine in the program overall, but is just broken inside of the set_completion_display_matches_hook callback. Why is this, and can I do something about it?

from Why don't I see errors from readline.set_completion_display_matches_hook?