Raise original import error in CLI vending of executors (#32931)

Small follow-up after #29055 - for better diagnostic of potential
future problems, it would be good to re-raise the original import
error, otherwise if the Import error results from some other issue
than Airflow version, we will get quite a bit of head scratching
trying to diagnose some of the resulting aftermath.

airflow/providers/celery/executors/celery_executor.py

@@ -68,6 +68,8 @@
             f"available in the 'airflow.executors' package. You should not use "
             f"the provider's executors in this version of Airflow."
         )
+    raise
+
 from airflow.configuration import conf
 from airflow.exceptions import AirflowTaskTimeout
 from airflow.executors.base_executor import BaseExecutor

airflow/providers/cncf/kubernetes/executors/kubernetes_executor.py

@@ -69,6 +69,7 @@
             f"available in the 'airflow.executors' package. You should not use "
             f"the provider's executors in this version of Airflow."
         )
+    raise
 from airflow.configuration import conf
 from airflow.executors.base_executor import BaseExecutor
 from airflow.providers.cncf.kubernetes.executors.kubernetes_executor_types import POD_EXECUTOR_DONE_KEY