Restore the original SIGINT handler after finishing.

        This should happen regardless of whether the progress display finishes
        normally, or gets interrupted.

def finish(self):
        """
        Restore the original SIGINT handler after finishing.

        This should happen regardless of whether the progress display finishes
        normally, or gets interrupted.
        """
        super(InterruptibleMixin, self).finish()
        signal(SIGINT, self.original_handler)