Adding import missing for the status code

Author: dayandavid

docs/api-guide/testing.md

@@ -353,6 +353,7 @@ REST framework also provides a test case class for isolating `urlpatterns` on a
 ## Example
 
     from django.urls import include, path, reverse
+    from rest_framework import status
     from rest_framework.test import APITestCase, URLPatternsTestCase