OS X 10.6.8 doesn't have it, while 10.10 does. I'm not sure when it was added.
It may be missing from other platforms as well.
This currently doesn't handle the string manipulation options (-f, -s and -w in
MinGW anyway), since there is currently no need for it. Since xrange defaults
to starting at 0 instead of 1, and treats the end as exclusive instead of
inclusive, the args need to be extracted instead of doing:
xrange(*[int(a) for a in sys.argv[1:]])
Therefore, the step might as well be added, even though there is no current use.
