Comment 2 for bug 1541914

I did a couple of trusty→ xenial upgrades but could not reproduce this.

The first error in that log was this:

dpkg: considering deconfiguration of init-system-helpers, which would be broken by installation of upstart ...
dpkg: yes, will deconfigure init-system-helpers (broken by upstart)
Preparing to unpack .../upstart_1.13.2-0ubuntu18_amd64.deb ...
De-configuring init-system-helpers (1.14) ...
Unpacking upstart (1.13.2-0ubuntu18) over (1.12.1-0ubuntu4.2) ...

which got introduced by http://launchpadlibrarian.net/222852012/upstart_1.13.2-0ubuntu16_1.13.2-0ubuntu17.diff.gz

This apparently leads to a dependency loop. The Replaces: must be kept, but we could drop the Breaks: to make apt's job of breaking such loops simpler.