Refs #23960 -- Documented how to restore absolute redirect URLs.

docs/releases/1.9.txt

@@ -794,6 +794,16 @@ no longer include the scheme and domain part of the URLs. For example,
 replaced by ``self.assertRedirects(response, '/some-url/')`` (unless the
 redirection specifically contained an absolute URL, of course).
 
+In the rare case that you need the old behavior (discovered with an ancient
+version of Apache with ``mod_scgi`` that interprets a relative redirect as an
+"internal redirect", you can restore it by writing a custom middleware::
+
+    class LocationHeaderFix(object):
+        def process_response(self, request, response):
+            if 'Location' in response:
+                response['Location'] = request.build_absolute_uri(response['Location'])
+            return response
+
 Dropped support for PostgreSQL 9.0
 ----------------------------------