Added a reason for skipping a test

wagtail/wagtaildocs/tests.py

@@ -599,7 +599,7 @@ class TestServeView(TestCase):
         self.assertEqual(response.status_code, 200)
         self.assertEqual(response['X-Sendfile'], os.path.join(settings.MEDIA_ROOT, self.document.file.name))
 
-    @unittest.skipIf(django.VERSION >= (1, 8))  # Under Django 1.8. It adds "http://" to beginning of Location when it shouldn't
+    @unittest.skipIf(django.VERSION >= (1, 8), "Fails on Django 1.8")  # Under Django 1.8. It adds "http://" to beginning of Location when it shouldn't
     @override_settings(SENDFILE_BACKEND='sendfile.backends.mod_wsgi', SENDFILE_ROOT=settings.MEDIA_ROOT, SENDFILE_URL=settings.MEDIA_URL[:-1])
     def test_sendfile_mod_wsgi_backend(self):
         self.clear_sendfile_cache()