#3643 add more checks to _testcapi to prevent segfaults

Author: Victor Stinner
Reviewer: Benjamin Peterson
diff --git a/Misc/NEWS b/Misc/NEWS
index 83f1c96..ae40187 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -17,6 +17,12 @@
 Library
 -------
 
+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 3.0b3?
 ===========================