Clean up logger to close out file handles.

        After this is called, writing to self.log will get logs ending up
        getting discarded.

def cleanup_logger(self):
        """Clean up logger to close out file handles.

        After this is called, writing to self.log will get logs ending up
        getting discarded.
        """
        self.log_handler.close()
        self.log.removeHandler(self.log_handler)