Log a non-fatal error message to stderr, which is repeated at program termination.

        :param msg: Message to be printed.
        :param repeat_at_end: Set to false if the message should be printed, but not repeated at program termination.

def error(self, msg, repeat_at_end=True):
        """Log a non-fatal error message to stderr, which is repeated at program termination.

        :param msg: Message to be printed.
        :param repeat_at_end: Set to false if the message should be printed, but not repeated at program termination."""
        print(msg, file=sys.stderr)
        if repeat_at_end:
            self.error_log.append(msg)