assertion diffs: slightly confusing full diff for range

[blueyed]

>       assert range(5) == range(7)
E       assert range(0, 5) == range(0, 7)
E         Right contains 2 more items, first extra item: 5
E         Full diff:
E         - range(0, 7)
E         ?          ^
E         + range(0, 5)
E         ?          ^

This is what pprint.pformat returns.
It could handle range classes in a special way and call list on them maybe before.