The attached patches implement the new "except V as N:" syntax and the solution outlined in http://mail.python.org/pipermail/python-3000/2007-January/005395.html for avoiding exception-related refcount cycles.

new_exceptions.patch is the implementation and tests.
fixup.patch adjusts the stdlib to use the new syntax.
doc_fixes.patch fixes documentation and some docs-related utilities missed by Guido's 2to3 code.

All patches are against r53289.

File Added: doc_fixes.patch

File Added: fixup.patch

Reviewing...  Seems the merge tfrom the 2.6 trunk that Thomas did made some changes to tarfile.py.

Did you have to manually patch anything up after running 2to3/refactor.py -f except on the entire stdlib?

patching file Lib/tarfile.py
Hunk #1 succeeded at 1540 (offset 38 lines).
Hunk #3 succeeded at 1573 (offset 38 lines).
Hunk #5 succeeded at 1745 (offset 38 lines).
Hunk #7 succeeded at 1786 (offset 38 lines).
Hunk #9 FAILED at 1795.
1 out of 9 hunks FAILED -- saving rejects to file Lib/tarfile.py.rej

For some strange reason, test_exceptions was wrong.  I'm guessing that the newly added test should be this:
 
    def testExceptionCleanup(self):
        # Make sure "except V as N" exceptions are cleaned up properly
        
        try:
            raise Exception()
        except Exception as e:
            self.failUnless(e)
        self.failIf('e' in locals())

(it had ', e' instead of 'as e', and there was an unneeded 'del e' after self.failUnless(e).)

I think there were only four files I had to patch manually after running 2to3; each used automatic exception unpacking.

2to3 successfully fixes Lib/tarfile.py (as of tarfile.py r53336, 2to3 r53339).

The 'del e' in testExceptionCleanup() was indeed needed; it was there to verify that the transformation was

    except V as N:
       try:
          ...
       finally:
          N = None
          del N

and not

    except V as N:
       try:
          ...
       finally:
          del N

Thanks!!

Submitted, with tarfile.py and test_exceptions.py corrected (kept the 'del e' in the latter).
Committed revision 53342.

Note: there is now a new test_hotshot failure, probably due to the different code generated for except clauses; I'm keeping this patch open for that.

Is it time to drop the unpacking (sequence) behavior from exceptions altogether, per Brett's PEP?  (That would be a new SF patch.)

The hotshot failure may have been related to magic number/bytecode differences, but since a "make clean" resolves the problem, the issue is considered closed (http://mail.python.org/pipermail/python-3000/2007-January/005501.html).