Once TaskGroups (https://airflow.readthedocs.io/en/latest/concepts.html#taskgroup) that would be released in Airflow 2.0 reach feature parity with SubDags and we have wide adoption and feedback from users about Taskgroups we should deprecate Subdags and remove them eventually in Airflow 3.0.

Discussion Thread: https://lists.apache.org/thread.html/ra52746f9c8274469d343b5f0251199de776e75ab75ded6830886fb6a%40%3Cdev.airflow.apache.org%3E
tests/operators/test_subdag_operator.py
"""
        When the DagRun failed during the execution, it raises an Airflow Exception.
        """
        dag = DAG('parent', default_args=default_args)
        subdag = DAG('parent.test', default_args=default_args)
        subdag_task = SubDagOperator(task_id='test', subdag=subdag, dag=dag, poke_interval=1)
        subdag.create_dagrun = Mock()
        subdag.create_dagrun.return_value = self.dag_run_running
        subdag_task._get_dagrun = Mock()
        subdag_task._get_dagrun.side_effect = [None, self.dag_run_failed, self.dag_run_failed]
        with pytest.raises(AirflowException):
            subdag_task.pre_execute(context={'execution_date': DEFAULT_DATE})
            subdag_task.execute(context={'execution_date': DEFAULT_DATE})
            subdag_task.post_execute(context={'execution_date': DEFAULT_DATE})
    def test_execute_skip_if_dagrun_success(self):