Update Kubernetes library version (#18797)

Previously we pinned this version as v12 as a change to Kube library
internals meant v1.Pod objects now have a logger object inside them, and
couldn't be pickled on Python 3.6.

To fix that we have "backported" the change in Python 3.7 to make Logger
objects be pickled "by name". (In Python 3.7 the change adds
`__reduce__` methods on to the Logger and RootLogger objects, but here
we achieve it `copyreg` stdlib module so we don't monkeypatch
anything.)

This fix is also applied in to airflow core in a separate commit, but we
also apply it here in the provider so that cncf.kubernetes client
library can be updated but still used with older versions of Airflow
that don't have this fix in.

(cherry picked from commit 7222f68)

airflow/providers/cncf/kubernetes/utils/pod_manager.py

@@ -40,7 +40,11 @@
 from airflow.utils.log.logging_mixin import LoggingMixin
 
 if TYPE_CHECKING:
-    from kubernetes.client.models.core_v1_event_list import CoreV1EventList
+    try:
+        # Kube >= 19
+        from kubernetes.client.models.core_v1_event_list import CoreV1EventList as V1EventList
+    except ImportError:
+        from kubernetes.client.models.v1_event_list import V1EventList
 
 
 class PodLaunchFailedException(AirflowException):
@@ -317,7 +321,7 @@ def read_pod_logs(
             raise
 
     @tenacity.retry(stop=tenacity.stop_after_attempt(3), wait=tenacity.wait_exponential(), reraise=True)
-    def read_pod_events(self, pod: V1Pod) -> "CoreV1EventList":
+    def read_pod_events(self, pod: V1Pod) -> "V1EventList":
         """Reads events from the POD"""
         try:
             return self._client.list_namespaced_event(

tests/kubernetes/test_client.py

@@ -59,5 +59,9 @@ def test_disable_verify_ssl(self):
 
         _disable_verify_ssl()
 
-        configuration = Configuration()
+        # Support wide range of kube client libraries
+        if hasattr(Configuration, 'get_default_copy'):
+            configuration = Configuration.get_default_copy()
+        else:
+            configuration = Configuration()
         self.assertFalse(configuration.verify_ssl)