The Kubernetes executor has surprisingly low test coverage: 64% 

https://codecov.io/gh/apache/airflow/src/master/airflow/executors/kubernetes_executor.py - looks like some of the "flush/end" code is not tested.

We might want to improve it.
tests/executors/test_kubernetes_executor.py
self, mock_adopt_completed_pods, mock_adopt_launched_task
    ):
        executor = self.kubernetes_executor
        mock_ti = mock.MagicMock(queued_by_job_id="1", external_executor_id="1", dag_id="dag", task_id="task")
        mock_kube_client = mock.MagicMock()
        mock_kube_client.list_namespaced_pod.return_value.items = []
        executor.kube_client = mock_kube_client
        tis_to_flush = executor.try_adopt_task_instances([mock_ti])
        assert tis_to_flush == [mock_ti]
        mock_adopt_launched_task.assert_not_called()
        mock_adopt_completed_pods.assert_called_once()
    @mock.patch('airflow.executors.kubernetes_executor.get_kube_client')
    def test_adopt_launched_task(self, mock_kube_client):