Document the fact that the 'test' package is meant only for use by Python
itself and not by others.

Closes issue 9255.
diff --git a/Misc/NEWS b/Misc/NEWS
index ef7988f..6cf5a7d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -1655,6 +1655,9 @@
 Documentation
 ------------
 
+- Issue 9255: Document that the 'test' package is meant for internal Python use
+  only.
+
 - A small wsgi server was added as Tools/scripts/serve.py, and is used to
   implement a local documentation server via 'make serve' in the doc directory.