Given that range() produced a list in the 2.x series (hence limited to
available memory), and xrange() uses int internally for its values (and
hence couldn't even cope with short ranges with values greater than
sys.maxint).

So my preference is to mimic the 2.x range's behaviour in this case by
raising an overflow error if the sequence is too long.

(From Python 2.5.1)

>>> range(2**99, 2**100)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OverflowError: range() result has too many items
>>> range(2**99, 2**99+5)
[633825300114114700748351602688L, 633825300114114700748351602689L,
633825300114114700748351602690L, 633825300114114700748351602691L,
633825300114114700748351602692L]
>>> xrange(2**99, 2**99+5)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OverflowError: long int too large to convert to int