Support Django 3.2 support (2)

In Django 3.2 CookieStorage stores messages in the RFC 6265 compliant
format [1][2]. This means that horizon messages pass through cookies are
encoded in a different way that messages are encrypted.

Previously horizon UT interpretes messages in cookies literally in its own way,
but the change on CookieStorage in Django 3.2 broke it. Horizon should not
depend on its own way. The suggested way I believe is to use a method defined
in django.contrib.messages.storage.cookie.CookieStorage.

[1] https://docs.djangoproject.com/en/3.2/releases/3.2/#miscellaneous
[2] 2d6179c819

Change-Id: I3e5e12265d0bc7b753bbe1f57acdd663b9dd3587

openstack_dashboard/dashboards/project/vg_snapshots/tests.py

@@ -71,11 +71,10 @@ class GroupSnapshotTests(test.TestCase):
                       args=[vg_snapshot.id])
         res = self.client.post(url, formData)
         self.assertNoFormErrors(res)
-        # There are a bunch of backslashes for formatting in the message from
-        # the response, so remove them when validating the error message.
-        self.assertIn('Unable to create group "%s" from snapshot.'
-                      % new_cg_name,
-                      res.cookies.output().replace('\\', ''))
+        self.assertCookieMessage(
+            res,
+            'Unable to create group "%s" from snapshot.' % new_cg_name,
+            'Expected failure.')
         self.assertRedirectsNoFollow(res, INDEX_URL)
 
         mock_group_snapshot_get.assert_called_once_with(

openstack_dashboard/dashboards/project/volume_groups/tests.py

@@ -108,8 +108,7 @@ class VolumeGroupTests(test.TestCase):
         res = self.client.post(url, formData)
         self.assertNoFormErrors(res)
         self.assertRedirectsNoFollow(res, INDEX_URL)
-        self.assertIn("Unable to create group.",
-                      res.cookies.output())
+        self.assertCookieMessage(res, "Unable to create group.")
 
         self.mock_extension_supported.assert_called_once_with(
             test.IsHttpRequest(), 'AvailabilityZones')

openstack_dashboard/test/helpers.py

@@ -24,6 +24,7 @@ import traceback
 from unittest import mock
 
 from django.conf import settings
+from django.contrib.messages.storage import cookie as cookie_storage
 from django.contrib.messages.storage import default_storage
 from django.core.handlers import wsgi
 from django.test.client import RequestFactory
@@ -38,6 +39,7 @@ from requests.packages.urllib3.connection import HTTPConnection
 
 from horizon import base
 from horizon import conf
+from horizon import exceptions
 from horizon.test import helpers as horizon_helpers
 from openstack_dashboard import api
 from openstack_dashboard import context_processors
@@ -438,6 +440,16 @@ class TestCase(horizon_helpers.TestCase):
                 len(errors), 0,
                 "No errors were found on the workflow")
 
+    def assertCookieMessage(self, response, expected_msg, detail_msg=None):
+        data = response.cookies["messages"]
+        storage = cookie_storage.CookieStorage(None)
+        messages = [m.message for m in storage._decode(data.value)]
+        if detail_msg is not None:
+            _expected = exceptions._append_detail(expected_msg, detail_msg)
+        else:
+            _expected = expected_msg
+        self.assertIn(_expected, messages)
+
 
 class BaseAdminViewTests(TestCase):
     """Sets an active user with the "admin" role.