Fix ValueError in list_namespaced_config_map

Make sure we set an empty dict/list if we don't get
any data from the server

Fixes #104

kubernetes/client/api_client.py

@@ -626,6 +626,8 @@ class ApiClient(object):
                and instance.attribute_map[attr] in data\
                and isinstance(data, (list, dict)):
                 value = data[instance.attribute_map[attr]]
+                if value is None:
+                    value = [] if isinstance(data, list) else {}
                 setattr(instance, attr, self.__deserialize(value, attr_type))
 
         return instance

kubernetes/e2e_test/test_client.py

@@ -187,6 +187,8 @@ class TestClient(unittest.TestCase):
         resp = api.delete_namespaced_config_map(
             name='test-configmap', body={}, namespace='default')
 
+        resp = api.list_namespaced_config_map('kube-system', pretty=True)
+        self.assertEqual([], resp.items)
 
     @unittest.skipUnless(
         _is_k8s_running(), "Kubernetes is not available")