bpo-41152: IDLE: always use UTF-8 for standard IO streams (GH-21214)

diff --git a/Lib/idlelib/NEWS.txt b/Lib/idlelib/NEWS.txt
index c270fcb..7ae29af 100644
--- a/Lib/idlelib/NEWS.txt
+++ b/Lib/idlelib/NEWS.txt
@@ -3,6 +3,9 @@
 ======================================
 
 
+bpo-41152: The encoding of ``stdin``, ``stdout`` and ``stderr`` in IDLE
+is now always UTF-8.
+
 bpo-41144: Make Open Module open a special module such as os.path.
 
 bpo-40723: Make test_idle pass when run after import.