minor error reporting patch

[David Brownell]

> This is not really something I like to do, since it means we're
> indirectly supporting bad programming habits.  However this particular
> patch is pretty innocuous, and it is hard to argue against it, so I am
> going to check it in.

Thanks.  It's more important for things like network errors, where the
JDK really has been deficient on mechanisms to report what just went
wrong.  This particular case is pretty minor, and "FileNotFound" is
more specific than the networking errors I was thinking of.


> There are certain kinds of bug compatibility changes we probably ought
> to reject.  We can do that on a case-by-case basis though.

Makes sense to me; I'd bias towards bug-compatibility.

- Dave