This may be the same bug as https://bugs.launchpad.net/ubuntu/+source/unattended-upgrades/+bug/1018367
I found this http://ubuntuforums.org/showthread.php?t=2005415&page=2&p=12070400#post12070400
Deleting /etc/apt/apt.conf.d/20auto-upgrades worked for me
This may be the same bug as https:/ /bugs.launchpad .net/ubuntu/ +source/ unattended- upgrades/ +bug/1018367
I found this http:// ubuntuforums. org/showthread. php?t=2005415& page=2& p=12070400# post12070400
Deleting /etc/apt/ apt.conf. d/20auto- upgrades worked for me