Comment 12 for bug 576255

This sounds like something to bring forward as a bug in dpkg... in fact, I've gone ahead and filed it as a feature request:

https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/622885

There may not be an obvious way to do this, so I think we're just going to have to deal with the occasional confused user filing bug reports like this until there's a better solution.