The upgrade of acpid to ver. 2.0.20-1 seems to be a bit problematical for systemd. On several (or all) of my half-dozen systems, I saw a hang of the ugprade at the point where the running acpid service was supposed to be shut down. On all but one system, I was able to resolve it with "dpkg --configure -a". On my Toshiba netbook, I could finish d-u, but the prior package would never be removed, so every d-u pulled in the new version, and then hung up trying to shut off the running service. "apt-get purge" could not remove it, either. This morning I fixed it by taking systemd-sysv off hold, letting sysvinit be installed, rebooting, and running the d-u in init 3. Then I reinstalled systemd-sysv and it's all OK.
This is just FYI if anyone else has the same problem with acpid.
EDIT 29 SEP: To clarify, this fix was necessary on both of my 32-bit installations and none of my 64-bit installations.