#3643 add a few more checks to _testcapi to prevent segfaults

Author: Victor Stinner
Reviewer: Benjamin Peterson
diff --git a/Misc/NEWS b/Misc/NEWS
index 07fc1f3..2ae121a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -25,6 +25,12 @@
 
 - Fixed two format strings in the _collections module.
 
+Extension Modules
+-----------------
+
+- Issue #3643: Added a few more checks to _testcapi to prevent segfaults by
+  exploitation of poor argument checking.
+
 
 What's New in Python 2.6 beta 3?
 ================================