[AIRFLOW-6020] Fix python 3 KubernetesExecutor iteritems exception (a…

…pache#6614)

airflow/executors/kubernetes_executor.py

@@ -274,7 +274,7 @@ def _run(self, kube_client, resource_version, worker_uuid, kube_config):
         if resource_version:
             kwargs['resource_version'] = resource_version
         if kube_config.kube_client_request_args:
-            for key, value in kube_config.kube_client_request_args.iteritems():
+            for key, value in kube_config.kube_client_request_args.items():
                 kwargs[key] = value
 
         last_resource_version = None
@@ -652,7 +652,7 @@ def clear_not_launched_queued_tasks(self, session=None):
             # pylint: enable=protected-access
             kwargs = dict(label_selector=dict_string)
             if self.kube_config.kube_client_request_args:
-                for key, value in self.kube_config.kube_client_request_args.iteritems():
+                for key, value in self.kube_config.kube_client_request_args.items():
                     kwargs[key] = value
             pod_list = self.kube_client.list_namespaced_pod(
                 self.kube_config.kube_namespace, **kwargs)