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**Description**

Related to the discussion here: https://github.com/apache/airflow/pull/8553#discussion_r416136954

Allow user to define expected terminal state. e.g. `JOB_STATE_CANCELLED` could be not treated as failure but expected terminal state.


<!-- A short description of your feature -->


@mock.patch("airflow.providers.google.cloud.operators.dataflow.DataflowHook")
    def test_execute(self, mock_hook):
        start_sql = DataflowStartSqlJobOperator(
            task_id="start_sql_query",
            job_name=TEST_SQL_JOB_NAME,
            query=TEST_SQL_QUERY,
            options=deepcopy(TEST_SQL_OPTIONS),
            location=TEST_LOCATION,
            do_xcom_push=True,
        )
        start_sql.execute(mock.MagicMock())
        mock_hook.assert_called_once_with(
            gcp_conn_id="google_cloud_default",
            drain_pipeline=False,
            impersonation_chain=None,
        )
        mock_hook.return_value.start_sql_job.assert_called_once_with(
            job_name=TEST_SQL_JOB_NAME,
            query=TEST_SQL_QUERY,
            options=TEST_SQL_OPTIONS,
            location=TEST_LOCATION,
            project_id=None,
            on_new_job_callback=mock.ANY,
        )
        start_sql.job = TEST_SQL_JOB
        start_sql.on_kill()
        mock_hook.return_value.cancel_job.assert_called_once_with(
            job_id="test-job-id", project_id=None, location=None
        )
class TestDataflowStopJobOperator: