Comment 3 for bug 2002168

I'd rather we have the implementation in update-manager reused by pro and not the other way around, the whole thing should be meaningful for users.

Notably apt has its own implementation of phased updates and phasing that update-manager and update -notifier also needs to switch to, but which is not yet exposed in python-apt.

We can't have multiple implementations of phased updates that each count slightly different because their languages have different RNG implementations.