[Python-3000] Implicit exception chaining (patch)

[Antoine Pitrou]

Hello,

In the true spirit of the anti-code retention meme launched by Guido, I've
posted a patch implementing the implicit exception chaining part of PEP 3134.
The core functionality is there, but its consequences on exception reporting
are still non-existent (no funky multi-traceback exception messages for you).

Interested people can read at: http://bugs.python.org/issue3108

Regards

Antoine.