Got the very basic functionality working!!
Probably there are some more bugs in the core ASP code, and telling it
to minimize errors doesn't seem to quite work, but disallowing them
does.

-Peter Mawhorter
Turns out I was discarding optimization statements entirely. Now that
that's changed (only directives are still discarded) the
optimization-based error debugging works! I also had to fiddle with
asp.py to get it to accept successful optimizations along with normal
SATISFIABLE results.