Creates temporary file to mark the task as `done`

def done(self):
        """
        Creates temporary file to mark the task as `done`
        """
        logger.info('Marking %s as done', self)

        fn = self.get_path()
        try:
            os.makedirs(os.path.dirname(fn))
        except OSError:
            pass
        open(fn, 'w').close()