[1.10.x] Added urlpatterns variable in docs/topics/http/urls.txt.

Backport of 91e9be45ed from master

docs/topics/http/urls.txt

@@ -822,7 +822,9 @@ For example::
         url(r'^(?P<pk>\d+)/$', views.DetailView.as_view(), name='detail'),
     ], 'polls')
 
-    url(r'^polls/', include(polls_patterns)),
+    urlpatterns = [
+        url(r'^polls/', include(polls_patterns)),
+    ]
 
 This will include the nominated URL patterns into the given application
 namespace.