Unspecific Exception for .localize() of non-existent local time

If you try to localize() a non-existent datetime like datetime.datetime(2008, 3, 9, 2, 30) to US/Pacific, you get an IndexError. It would be much nicer if there were a custom Exception type for this case. Reusing AmbiguousTimeError would be OK but I think a distinct Exception type would be better. If you set is_dst=None then you do get an AmbiguousTimeError but this is not really correct since the time is non-existent rather than ambiguous and the handling of user input of such a time would be different than user input of an ambiguous time at the end of dst.