patch #1668: clarify envvar docs; rename THREADDEBUG to PYTHONTHREADDEBUG.
diff --git a/Misc/NEWS b/Misc/NEWS
index dbc0034..e76e733 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@
 Core and builtins
 -----------------
 
+- Patch #1668: renamed THREADDEBUG envvar to PYTHONTHREADDEBUG.
+
 - Patch #602345: Add -B command line option, PYTHONDONTWRITEBYTECODE envvar
   and sys.dont_write_bytecode attribute. All these can be set to forbid Python
   to attempt to write compiled bytecode files.