I guess there needs to be a decision on whether to make range objects of 
length >= PY_SSIZE_T_MAX illegal; perhaps more discussion on python-dev 
would be worthwhile?

I can see three options, besides leaving things as they are:

(1) make large ranges illegal, as with this patch
(2) make large ranges legal, but don't allow indexing with indices
larger than PY_SSIZE_T_MAX.
(3) allow large ranges *and* large indices.

Option 3 seems to me like the ideal from the users' point of view, but I'm 
not sure whether it's easy/possible to implement it given that sq_item 
receives a Py_ssize_t for the index.

Option 2 seems messy:  half of one thing and half of the other, but I 
think it would be easy to implement.  This is what I'd personally prefer 
if Option 3 isn't feasible.

If Option 1 is indeed the preferred option, then the patch looks good to 
me, and works for me on OS X 10.5.  (Minor nitpick: it introduces some 
extra tab characters.)

Whatever happens, we probably also need a documentation update explaining 
the limitations on range.