Release notes blurb for 804366327d728d23a9f7a25ff77a6eed3c9f9323.

docs/releases/1.6.txt

@@ -127,6 +127,10 @@ Minor features
 
 * The isolation level can be customized under PostgreSQL.
 
+* The :ttag:`blocktrans` template tag now respects
+  :setting:`TEMPLATE_STRING_IF_INVALID` for variables not present in the
+  context, just like other template constructs.
+
 Backwards incompatible changes in 1.6
 =====================================