Update whatsnew

Author: gaogaotiantian

Doc/whatsnew/3.15.rst

@@ -788,6 +788,14 @@ base64
   (Contributed by Gregory P. Smith in :gh:`146311`.)
 
 
+bdb
+---
+* :exc:`bdb.BdbQuit` is now a subclass of :exc:`BaseException`, instead of
+  :exc:`Exception`, to allow it to be used for cleanly exiting the debugger without
+  being accidentally caught by user code.
+  (Contributed by Tian Gao in :gh:`149337`.)
+
+
 binascii
 --------