tests.urls: handle optional coreapi

tests/urls.py

@@ -5,8 +5,12 @@ We need only the docs urls for DocumentationRenderer tests.
 """
 from django.conf.urls import url
 
+from rest_framework.compat import coreapi
 from rest_framework.documentation import include_docs_urls
 
+if coreapi:
     urlpatterns = [
         url(r'^docs/', include_docs_urls(title='Test Suite API')),
     ]
+else:
+    urlpatterns = []