Builddep notifies apt-get update instead of requiring it

as the title says, builddep notifies apt-get update instead of requiring it, which doesn't make much sense. In almost every case, you want apt-get update to be executed before builddep.

The problem I ran into is a huge dependency cycle because of apt-get update. Builddep had to be executed after sources being added which after a lot of trying I concluded to not be possible. ([serverfault here](http://serverfault.com/questions/610356/puppet-class-node-dependencies))

Changing `notify` to `require` solves this dependency cycle for me.

Any thoughts on this?