[Python-3000] Automated py3k doc builds

[Collin Winter]

I just discovered that the p3yk/ branch can't do a docs build because
almost none of the code in Doc/tools/ is valid Python 3 [1]. How hard
would it be to set up something akin to http://docs.python.org/dev/
for p3yk (ie, regular, automated builds), if only to catch problems
like this sooner?

Collin Winter

[1] - a patch to correct Doc/tools/* syntax is available as an
attachment on bug #1684811.