Comment 2 for bug 1768379

Liberal application of dpkg -i /var/cache/apt/archives/.... has gotten me much further, but this is a real sticking point:

225 upgraded, 122 newly installed, 315 to remove and 2028 not upgraded.
16 not fully installed or removed.
Need to get 0 B/254 MB of archives.
After this operation, 389 MB disk space will be freed.
Do you want to continue? [Y/n]
Extracting templates from packages: 100%
Preconfiguring packages ...
(Reading database ... 374078 files and directories currently installed.)
Removing systemd-shim (9-1bzr4ubuntu1) ...
Removing 'diversion of /usr/share/dbus-1/system-services/org.freedesktop.systemd1.service to /usr/share/dbus-1/system-services/org.freedesktop.systemd1.service.systemd by systemd-shim'
dpkg-divert: error: rename involves overwriting '/usr/share/dbus-1/system-services/org.freedesktop.systemd1.service' with
  different file '/usr/share/dbus-1/system-services/org.freedesktop.systemd1.service.systemd', not allowed
dpkg: error processing package systemd-shim (--remove):
 subprocess installed post-removal script returned error exit status 2
Errors were encountered while processing:
 systemd-shim
E: Sub-process /usr/bin/dpkg returned an error code (1)

That diversion does exist:

$ dpkg-divert --list | grep shim
diversion of /usr/share/dbus-1/system-services/org.freedesktop.systemd1.service to /usr/share/dbus-1/system-services/org.freedesktop.systemd1.service.systemd by systemd-shim

and those files exist, with different contents:

ebf27f9c1e4b77939498616a1500e6a2cdb00862c116294d9844f5ddef8d0ca7 /usr/share/dbus-1/system-services/org.freedesktop.systemd1.service
37a68d852e39114b9691001fc91c9db098e506e077a324329c46159020ab3f39 /usr/share/dbus-1/system-services/org.freedesktop.systemd1.service.systemd