Init policy in pecan after hook as well

policy.init() is called in the before hook, but this isn't
invoked on GET calls so if the first call a thread receives
is a GET call, we can end up with an uninitialized policy
enforcer and get a traceback.

This just calls policy.init() in the after hook as well.

Change-Id: I29ebc9a91b98a27e707d5b35ad1a24a26e8c8f44
Closes-Bug: #1671267
(cherry picked from commit 4c40016dfb)

neutron/pecan_wsgi/hooks/policy_enforcement.py

@@ -163,6 +163,7 @@ class PolicyHook(hooks.PecanHook):
             return
         if not data or (resource not in data and collection not in data):
             return
+        policy.init()
         is_single = resource in data
         action_type = pecan_constants.ACTION_MAP[state.request.method]
         if action_type == 'get':

neutron/tests/functional/pecan_wsgi/test_hooks.py

@@ -221,6 +221,17 @@ class TestPolicyEnforcementHook(test_functional.PecanFunctionalTest):
         json_response = jsonutils.loads(response.body)
         self.assertNotIn('restricted_attr', json_response['mehs'][0])
 
+    def test_after_inits_policy(self):
+        self.mock_plugin.get_mehs.return_value = [{
+            'id': 'xxx',
+            'attr': 'meh',
+            'restricted_attr': '',
+            'tenant_id': 'tenid'}]
+        policy.reset()
+        response = self.app.get('/v2.0/mehs',
+                                headers={'X-Project-Id': 'tenid'})
+        self.assertEqual(200, response.status_int)
+
 
 class TestMetricsNotifierHook(test_functional.PecanFunctionalTest):