Comment 3 for bug 349469

It would be entirely unhelpful if dpkg checked the debconf lock; you'd just get much the same failure slightly further up.

Maybe apt could check, but I think this might be more realistic for something that's intended to be much smarter, such as update-manager, so reassigning there. However, note that it is not actually possible to check this correctly outside debconf right now, as debconf does not necessarily use the same database in all installations. I recommend not fixing this in haste.