take care of empty kube_config files

config/kube_config.py

@@ -682,6 +682,9 @@ def _load_config_from_file_like_object(self, string):
         else:
             config = yaml.safe_load(string.read())
 
+        if config is None:
+            raise ConfigException(
+                'Invalid kube-config.')
         if self.config_merged is None:
             self.config_merged = copy.deepcopy(config)
         # doesn't need to do any further merging
@@ -699,6 +702,11 @@ def load_config(self, path):
         with open(path) as f:
             config = yaml.safe_load(f)
 
+        if config is None:
+            raise ConfigException(
+                'Invalid kube-config. '
+                '%s file is empty' % path)
+
         if self.config_merged is None:
             config_merged = copy.deepcopy(config)
             for item in ('clusters', 'contexts', 'users'):

config/kube_config_test.py

@@ -1290,6 +1290,15 @@ def test_load_kube_config_from_dict(self):
                                    client_configuration=actual)
         self.assertEqual(expected, actual)
 
+    def test_load_kube_config_from_empty_file(self):
+        config_file_like_object = io.StringIO()
+        self.assertRaises(ConfigException, load_kube_config, config_file_like_object)
+
+    def test_load_kube_config_from_empty_file_like_object(self):
+        config_file = self._create_temp_file(
+            yaml.safe_dump(None))
+        self.assertRaises(ConfigException, load_kube_config, config_file)
+
     def test_list_kube_config_contexts(self):
         config_file = self._create_temp_file(
             yaml.safe_dump(self.TEST_KUBE_CONFIG))