If you *must* support the two-arg flavor (which I've never actually seen outside this discussion), I'd suggest not documenting it as a backward compatibility, only that it will disappear in 1.7. This can be done fairly easily and cleanly in the library reference.
Yes, I must. Can you fix up the docs?
--Guido van Rossum (home page: http://www.python.org/%7Eguido/)