exception message rather than the whole exception tuple. This changes
./ndiff: ('option --foo not recognized', 'foo')
to
./ndiff: option --foo not recognized
happens when a host was scanned in the A scan but wasn't scanned in the B scan.
I previously had it ignore such changes using the logic that the diff should be
like scan aggregation: no new information means no state change. But I think
it's more useful to see those changes in which hosts were scanned.
This is analogous to r10263, which did the same thing for port state changes.
did this with the idea of making diffing like scan aggregation, with known
characteristics carrying forward through unknown. But it can be confusing. I
think when you diff
nmap scanme.nmap.org
and
nmap -F scanme.nmap.org
you want to see that the gopher port changes from closed to unknown, because
it's not scanned by fast scan.
