Replace response body in after hook for 404 error

Closes-Bug: 2130972

Change-Id: I662b3eb7fb8c17d0ad30b10e8537d4a142003256
Signed-off-by: Sergey Kraynev <sergejyit@gmail.com>
(cherry picked from commit d95e3e5eaf)

neutron/pecan_wsgi/hooks/policy_enforcement.py

@@ -18,6 +18,7 @@ import copy
 from neutron_lib import constants as const
 from oslo_log import log as logging
 from oslo_policy import policy as oslo_policy
+from oslo_serialization import jsonutils
 from oslo_utils import excutils
 from pecan import hooks
 import webob
@@ -195,6 +196,14 @@ class PolicyHook(hooks.PecanHook):
             # we have to set the status_code here to prevent the catch_errors
             # middleware from turning this into a 500.
             state.response.status_code = 404
+            # replace the original body on NotFound body
+            error_message = {
+                'type': 'HTTPNotFound',
+                'message': 'The resource could not be found.',
+                'detail': ''
+            }
+            state.response.text = jsonutils.dumps(error_message)
+            state.response.content_type = 'application/json'
             return
 
         if is_single:

neutron/tests/functional/pecan_wsgi/test_hooks.py

@@ -288,6 +288,12 @@ class TestPolicyEnforcementHook(test_functional.PecanFunctionalTest):
                                 headers={'X-Project-Id': 'tenid'},
                                 expect_errors=True)
         self.assertEqual(404, response.status_int)
+        self.assertEqual(
+            {
+                'type': 'HTTPNotFound',
+                'message': 'The resource could not be found.',
+                'detail': ''
+            }, jsonutils.loads(response.body))
         self.assertEqual(1, self.mock_plugin.get_meh.call_count)
 
     def test_after_on_get_excludes_admin_attribute(self):