Add python3 support?

Hello,

I don't know if it is linked to python 3.1, but when I install mercurial_keyring with it, I get the following error: running install running build running build_py creating build creating build/lib copying mercurial_keyring.py -> build/lib running install_lib creating /tmp/yaourt-tmp-victor/aur-python-mercurial_keyring/pkg/usr creating /tmp/yaourt-tmp-victor/aur-python-mercurial_keyring/pkg/usr/lib creating /tmp/yaourt-tmp-victor/aur-python-mercurial_keyring/pkg/usr/lib/python3.1 creating /tmp/yaourt-tmp-victor/aur-python-mercurial_keyring/pkg/usr/lib/python3.1/site-packages copying build/lib/mercurial_keyring.py -> /tmp/yaourt-tmp-victor/aur-python-mercurial_keyring/pkg/usr/lib/python3.1/site-packages byte-compiling /tmp/yaourt-tmp-victor/aur-python-mercurial_keyring/pkg/usr/lib/python3.1/site-packages/mercurial_keyring.py to mercurial_keyring.pyc File "/usr/lib/python3.1/site-packages/mercurial_keyring.py", line 302 except smtplib.SMTPException, inst: ^ SyntaxError: invalid syntax

It was not appearing with python 2.6 :)

(sorry for the bad formatting…)

I guess it could be linked to: http://docs.python.org/release/3.0.1/whatsnew/2.6.html#pep-3110

As far as I know Mercurial is not python3k compatible, so this change is pointless. I initially pulled the offered change which changes extension syntax, but it makes extension no longer 2.4- and 2.5- compatible so I am just to revert it.

The right order is 1) port Mercurial 2) port keyring 3) port mercurial_keyring.