bpo-23894: add Misc/NEWS entry. (#2256)

Author: ned-deily

Misc/NEWS

@@ -365,6 +365,8 @@ Extension Modules
 Library
 -------
 
+- bpo-23894: lib2to3 now recognizes ``rb'...'`` and ``f'...'`` strings.
+
 - [Security] bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes
   of CVE-2016-0718 and CVE-2016-4472. See
   https://sourceforge.net/p/expat/bugs/537/ for more information.