Issue #12791: Break reference cycles early when a generator exits with an exception.

diff --cc Lib/test/test_exceptions.py
Simple merge

diff --cc Misc/NEWS
index 36c9b8b181d53c2f3fe6f7cd75fe635202a695ab,f8c135f66331226fc2558e01c9030d86e6bd3d12..7dc106afee10d6434b30b4e3c661f66a0e068ab7
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -10,13 -10,28 +10,16 @@@ What's New in Python 3.3 Alpha 1
  Core and Builtins
  -----------------
  
 -- Issue #12266: Fix str.capitalize() to correctly uppercase/lowercase
 -  titlecased and cased non-letter characters.
 -
 -Library
 --------
 -
 -- Issue #12326: sys.platform is now always 'linux2' on Linux, even if Python
 -  is compiled on Linux 3.
 -
 -- Issue #12650: Fix a race condition where a subprocess.Popen could leak
 -  resources (FD/zombie) when killed at the wrong time.
+ - Issue #12791: Break reference cycles early when a generator exits with
+   an exception.
+ 
 +- Issue #12773: Make __doc__ mutable on user-defined classes.
  
 -What's New in Python 3.2.2?
 -===========================
 +- Issue #12766: Raise an ValueError when creating a class with a class variable
 +  that conflicts with a name in __slots__.
  
 -*Release date: XX-XXX-2011*
 -
 -Core and Builtins
 ------------------
 +- Issue #12266: Fix str.capitalize() to correctly uppercase/lowercase
 +  titlecased and cased non-letter characters.
  
  - Issue #12732: In narrow unicode builds, allow Unicode identifiers which fall
    outside the BMP.

diff --cc Objects/genobject.c
Simple merge