Determines if task directory exists.

            `task_name`
                Task name.

            Returns ``True`` if task exists.

def exists(self, task_name):
        """ Determines if task directory exists.

            `task_name`
                Task name.

            Returns ``True`` if task exists.
            """

        try:
            return os.path.exists(self._get_task_dir(task_name))

        except OSError:
            return False