Fix KeyError when KPO exits too soon

[vchiapaikeo]

On occasions where the pod terminates quickly on pod failure, instead of an AirflowException being raised, we see a KeyError exception:

2024-02-17, 08:35:59 EST] {base.py:83} INFO - Using connection ID 'google_cloud_default' for task execution.
[2024-02-17, 08:35:59 EST] {credentials_provider.py:353} INFO - Getting connection using `google.auth.default()` since no explicit credentials are provided.
[2024-02-17, 08:36:00 EST] {pod_manager.py:798} INFO - Running command... if [ -s /***/xcom/return.json ]; then cat /***/xcom/return.json; else echo __***_xcom_result_empty__; fi
[2024-02-17, 08:36:00 EST] {pod_manager.py:798} INFO - Running command... kill -s SIGINT 1
[2024-02-17, 08:36:00 EST] {pod.py:559} INFO - xcom result file is empty.
[2024-02-17, 08:36:00 EST] {pod.py:709} INFO - Got event: {'status': 'failed', 'namespace': '***-default', 'name': 'fail-quzr387j'}
[2024-02-17, 08:36:00 EST] {pod.py:773} INFO - Container logs: + sleep 2
[2024-02-17, 08:36:00 EST] {pod.py:773} INFO - Container logs: + exit 1
[2024-02-17, 08:36:00 EST] {pod.py:773} INFO - Container logs: 
[2024-02-17, 08:36:00 EST] {pod_manager.py:616} INFO - Pod fail-quzr387j has phase Running
[2024-02-17, 08:36:03 EST] {pod.py:907} INFO - Skipping deleting pod: fail-quzr387j
[2024-02-17, 08:36:03 EST] {taskinstance.py:2751} ERROR - Task failed with exception
Traceback (most recent call last):
  File "/opt/airflow/airflow/providers/cncf/kubernetes/operators/pod.py", line 711, in trigger_reentry
    message = event.get("stack_trace", event["message"])
KeyError: 'message'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/opt/airflow/airflow/models/taskinstance.py", line 446, in _execute_task
    result = _execute_callable(context=context, **execute_callable_kwargs)
  File "/opt/airflow/airflow/models/taskinstance.py", line 416, in _execute_callable
    return execute_callable(context=context, **execute_callable_kwargs)
  File "/opt/airflow/airflow/models/baseoperator.py", line 1623, in resume_execution
    return execute_callable(context)
  File "/opt/airflow/airflow/providers/google/cloud/operators/kubernetes_engine.py", line 789, in execute_complete
    return super().execute_complete(context, event, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/deprecated/classic.py", line 285, in wrapper_function
    return wrapped_(*args_, **kwargs_)
  File "/opt/airflow/airflow/providers/cncf/kubernetes/operators/pod.py", line 762, in execute_complete
    self.trigger_reentry(context=context, event=event)
  File "/opt/airflow/airflow/providers/cncf/kubernetes/operators/pod.py", line 740, in trigger_reentry
    self._clean(event)
  File "/opt/airflow/airflow/providers/cncf/kubernetes/operators/pod.py", line 755, in _clean
    self.post_complete_action(
  File "/opt/airflow/airflow/providers/cncf/kubernetes/operators/pod.py", line 783, in post_complete_action
    self.cleanup(
  File "/opt/airflow/airflow/providers/cncf/kubernetes/operators/pod.py", line 834, in cleanup
    raise AirflowException(
airflow.exceptions.AirflowException: Pod fail-quzr387j returned a failure.

The reason for this is because this TriggerEvent payload does not pass a message field which is expected here.

Granted, this is not really a big problem. The next line is the raise anyways. It's just a bit confusing to the user.

This fixes the missing message KeyError so that we see the proper exception getting raised:

---

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[pankajastro]

LGTM