Remove some uses of assertContains from username changes api

misago/users/tests/test_usernamechanges_api.py

@@ -42,21 +42,25 @@ class UsernameChangesApiTests(AuthenticatedUserTestCase):
         override_acl(self.user, {'can_see_users_name_history': False})
 
         response = self.client.get('%s?user=%s&search=new' % (self.link, self.user.pk))
-
         self.assertEqual(response.status_code, 200)
         self.assertContains(response, self.user.username)
 
         response = self.client.get('%s?user=%s&search=usernew' % (self.link, self.user.pk))
-
         self.assertEqual(response.status_code, 200)
-        self.assertContains(response, '[]')
+        self.assertEqual(response.json()["count"], 0)
 
     def test_list_denies_permission(self):
         """list denies permission for other user (or all) if no access"""
         override_acl(self.user, {'can_see_users_name_history': False})
 
         response = self.client.get('%s?user=%s' % (self.link, self.user.pk + 1))
-        self.assertContains(response, "don't have permission to", status_code=403)
+        self.assertEqual(response.status_code, 403)
+        self.assertEqual(response.json(), {
+            "detail": "You don't have permission to see other users name history."
+        })
 
         response = self.client.get(self.link)
-        self.assertContains(response, "don't have permission to", status_code=403)
+        self.assertEqual(response.status_code, 403)
+        self.assertEqual(response.json(), {
+            "detail": "You don't have permission to see other users name history."
+        })