There fixed it for you :)
LE: python 2.5 -> 2.4 (bconway was right)
A.) RHEL 5.x (by default) comes with Python 2.4, not 2.5.
B.) Yes you can. It is required in 3.x, though.
LE: python 2.5 -> 2.4 (bconway was right)