Comment 17 for bug 1269177

The update in artful-proposed also resolves the issue for me.

bdmurray@clean-artful-amd64:~$ sudo apt-get install unattended-upgrades
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  bsd-mailx mail-transport-agent needrestart
The following packages will be upgraded:
  unattended-upgrades
1 upgraded, 0 newly installed, 0 to remove and 36 not upgraded.
Need to get 37.4 kB of archives.
After this operation, 4,096 B of additional disk space will be used.
Get:1 http://192.168.10.7/ubuntu artful-proposed/main amd64 unattended-upgrades all 0.98ubuntu1.1 [37.4 kB]
Fetched 37.4 kB in 0s (518 kB/s)
Preconfiguring packages ...
(Reading database ... 166406 files and directories currently installed.)
Preparing to unpack .../unattended-upgrades_0.98ubuntu1.1_all.deb ...
Unpacking unattended-upgrades (0.98ubuntu1.1) over (0.98ubuntu1) ...
Processing triggers for ureadahead (0.100.0-20) ...
Processing triggers for systemd (234-2ubuntu12.1) ...
Setting up unattended-upgrades (0.98ubuntu1.1) ...
Processing triggers for man-db (2.7.6.1-2) ...
bdmurray@clean-artful-amd64:~$ sudo touch /var/run/reboot-required
bdmurray@clean-artful-amd64:~$ sudo unattended-upgrades --dry-run
bdmurray@clean-artful-amd64:~$