Here's the log from running `sudo unattended-upgrade --dry-run --debug` in case it's helpful:

2016-07-07 16:58:53,281 INFO Initial blacklisted packages:
2016-07-07 16:58:53,282 INFO Starting unattended upgrades script
2016-07-07 16:58:53,282 INFO Allowed origins are: ['o=Ubuntu,a=precise-security']
2016-07-07 16:58:53,745 DEBUG adjusting candidate version: '<Version: package:'apt' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:53,761 DEBUG adjusting candidate version: '<Version: package:'apt-transport-https' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:53,771 DEBUG adjusting candidate version: '<Version: package:'apt-utils' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:53,821 DEBUG adjusting candidate version: '<Version: package:'dpkg' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:53,843 DEBUG adjusting candidate version: '<Version: package:'dpkg-dev' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:53,958 DEBUG adjusting candidate version: '<Version: package:'libapt-inst1.4' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:53,970 DEBUG adjusting candidate version: '<Version: package:'libapt-pkg4.12' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:54,013 DEBUG adjusting candidate version: '<Version: package:'libdpkg-perl' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:54,277 DEBUG adjusting candidate version: '<Version: package:'ntp' version:'1:4.2.6.p3+dfsg-1ubuntu3.6'>'
2016-07-07 16:58:54,291 DEBUG adjusting candidate version: '<Version: package:'ntpdate' version:'1:4.2.6.p3+dfsg-1ubuntu3.6'>'
2016-07-07 16:58:54,340 DEBUG adjusting candidate version: '<Version: package:'puppet' version:'2.7.11-1ubuntu2.7'>'
2016-07-07 16:58:54,362 DEBUG adjusting candidate version: '<Version: package:'puppet-common' version:'2.7.11-1ubuntu2.7'>'
2016-07-07 16:58:54,449 DEBUG adjusting candidate version: '<Version: package:'unattended-upgrades' version:'0.76ubuntu1.1'>'
2016-07-07 16:58:55,110 DEBUG Checking: cloud-init (["<Origin component:'main' archive:'precise-updates' origin:'Ubuntu' label:'Ubuntu' site:'us-east-1.ec2.archive.ubuntu.com' isTrusted:True>"])
2016-07-07 16:58:55,138 DEBUG Checking: facter (["<Origin component:'main' archive:'precise' origin:'Puppetlabs' label:'Puppetlabs' site:'apt.puppetlabs.com' isTrusted:True>"])
2016-07-07 16:58:55,178 DEBUG Checking: grub-legacy-ec2 (["<Origin component:'main' archive:'precise-updates' origin:'Ubuntu' label:'Ubuntu' site:'us-east-1.ec2.archive.ubuntu.com' isTrusted:True>"])
2016-07-07 16:58:55,193 DEBUG Checking: instrumental-tools (["<Origin component:'main' archive:'precise' origin:'https://packagecloud.io/expectedbehavior/instrumental' label:'instrumental' site:'packagecloud.io' isTrusted:True>"])
2016-07-07 16:58:55,401 DEBUG Checking: libruby2.0 (["<Origin component:'main' archive:'precise' origin:'LP-PPA-brightbox-ruby-ng' label:'Brightbox Ruby NG' site:'ppa.launchpad.net' isTrusted:True>"])
2016-07-07 16:58:55,487 DEBUG Checking: linux-headers-virtual (["<Origin component:'main' archive:'precise-updates' origin:'Ubuntu' label:'Ubuntu' site:'us-east-1.ec2.archive.ubuntu.com' isTrusted:True>", "<Origin component:'main' archive:'precise-security' origin:'Ubuntu' label:'Ubuntu' site:'security.ubuntu.com' isTrusted:True>"])
2016-07-07 16:58:55,957 DEBUG pkg 'linux-headers-3.2.0-105' not in allowed origin
2016-07-07 16:58:55,958 DEBUG sanity check failed
2016-07-07 16:58:56,173 DEBUG adjusting candidate version: '<Version: package:'apt' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:56,174 DEBUG adjusting candidate version: '<Version: package:'apt-transport-https' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:56,174 DEBUG adjusting candidate version: '<Version: package:'apt-utils' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:56,214 DEBUG adjusting candidate version: '<Version: package:'dpkg' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:56,224 DEBUG adjusting candidate version: '<Version: package:'dpkg-dev' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:56,330 DEBUG adjusting candidate version: '<Version: package:'libapt-inst1.4' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:56,330 DEBUG adjusting candidate version: '<Version: package:'libapt-pkg4.12' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:56,364 DEBUG adjusting candidate version: '<Version: package:'libdpkg-perl' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:56,619 DEBUG adjusting candidate version: '<Version: package:'ntp' version:'1:4.2.6.p3+dfsg-1ubuntu3.6'>'
2016-07-07 16:58:56,620 DEBUG adjusting candidate version: '<Version: package:'ntpdate' version:'1:4.2.6.p3+dfsg-1ubuntu3.6'>'
2016-07-07 16:58:56,659 DEBUG adjusting candidate version: '<Version: package:'puppet' version:'2.7.11-1ubuntu2.7'>'
2016-07-07 16:58:56,670 DEBUG adjusting candidate version: '<Version: package:'puppet-common' version:'2.7.11-1ubuntu2.7'>'
2016-07-07 16:58:56,748 DEBUG adjusting candidate version: '<Version: package:'unattended-upgrades' version:'0.76ubuntu1.1'>'
2016-07-07 16:58:56,785 DEBUG Checking: linux-image-virtual (["<Origin component:'main' archive:'precise-updates' origin:'Ubuntu' label:'Ubuntu' site:'us-east-1.ec2.archive.ubuntu.com' isTrusted:True>", "<Origin component:'main' archive:'precise-security' origin:'Ubuntu' label:'Ubuntu' site:'security.ubuntu.com' isTrusted:True>"])
2016-07-07 16:58:57,253 DEBUG pkg 'linux-headers-3.2.0-105' not in allowed origin
2016-07-07 16:58:57,253 DEBUG sanity check failed
2016-07-07 16:58:57,459 DEBUG adjusting candidate version: '<Version: package:'apt' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:57,460 DEBUG adjusting candidate version: '<Version: package:'apt-transport-https' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:57,461 DEBUG adjusting candidate version: '<Version: package:'apt-utils' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:57,499 DEBUG adjusting candidate version: '<Version: package:'dpkg' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:57,509 DEBUG adjusting candidate version: '<Version: package:'dpkg-dev' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:57,613 DEBUG adjusting candidate version: '<Version: package:'libapt-inst1.4' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:57,614 DEBUG adjusting candidate version: '<Version: package:'libapt-pkg4.12' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:57,647 DEBUG adjusting candidate version: '<Version: package:'libdpkg-perl' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:57,902 DEBUG adjusting candidate version: '<Version: package:'ntp' version:'1:4.2.6.p3+dfsg-1ubuntu3.6'>'
2016-07-07 16:58:57,903 DEBUG adjusting candidate version: '<Version: package:'ntpdate' version:'1:4.2.6.p3+dfsg-1ubuntu3.6'>'
2016-07-07 16:58:57,941 DEBUG adjusting candidate version: '<Version: package:'puppet' version:'2.7.11-1ubuntu2.7'>'
2016-07-07 16:58:57,953 DEBUG adjusting candidate version: '<Version: package:'puppet-common' version:'2.7.11-1ubuntu2.7'>'
2016-07-07 16:58:58,030 DEBUG adjusting candidate version: '<Version: package:'unattended-upgrades' version:'0.76ubuntu1.1'>'
2016-07-07 16:58:58,066 DEBUG Checking: linux-virtual (["<Origin component:'main' archive:'precise-updates' origin:'Ubuntu' label:'Ubuntu' site:'us-east-1.ec2.archive.ubuntu.com' isTrusted:True>", "<Origin component:'main' archive:'precise-security' origin:'Ubuntu' label:'Ubuntu' site:'security.ubuntu.com' isTrusted:True>"])
2016-07-07 16:58:58,490 DEBUG pkg 'linux-headers-3.2.0-105' not in allowed origin
2016-07-07 16:58:58,490 DEBUG sanity check failed
2016-07-07 16:58:58,699 DEBUG adjusting candidate version: '<Version: package:'apt' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:58,700 DEBUG adjusting candidate version: '<Version: package:'apt-transport-https' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:58,701 DEBUG adjusting candidate version: '<Version: package:'apt-utils' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:58,739 DEBUG adjusting candidate version: '<Version: package:'dpkg' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:58,749 DEBUG adjusting candidate version: '<Version: package:'dpkg-dev' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:58,853 DEBUG adjusting candidate version: '<Version: package:'libapt-inst1.4' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:58,854 DEBUG adjusting candidate version: '<Version: package:'libapt-pkg4.12' version:'0.8.16~exp12ubuntu10.21'>'
2016-07-07 16:58:58,887 DEBUG adjusting candidate version: '<Version: package:'libdpkg-perl' version:'1.16.1.2ubuntu7.7'>'
2016-07-07 16:58:59,142 DEBUG adjusting candidate version: '<Version: package:'ntp' version:'1:4.2.6.p3+dfsg-1ubuntu3.6'>'
2016-07-07 16:58:59,143 DEBUG adjusting candidate version: '<Version: package:'ntpdate' version:'1:4.2.6.p3+dfsg-1ubuntu3.6'>'
2016-07-07 16:58:59,181 DEBUG adjusting candidate version: '<Version: package:'puppet' version:'2.7.11-1ubuntu2.7'>'
2016-07-07 16:58:59,193 DEBUG adjusting candidate version: '<Version: package:'puppet-common' version:'2.7.11-1ubuntu2.7'>'
2016-07-07 16:58:59,270 DEBUG adjusting candidate version: '<Version: package:'unattended-upgrades' version:'0.76ubuntu1.1'>'
2016-07-07 16:58:59,355 DEBUG Checking: psmisc (["<Origin component:'main' archive:'precise-updates' origin:'Ubuntu' label:'Ubuntu' site:'us-east-1.ec2.archive.ubuntu.com' isTrusted:True>"])
2016-07-07 16:58:59,357 DEBUG Checking: puppetlabs-release (["<Origin component:'main' archive:'precise' origin:'Puppetlabs' label:'Puppetlabs' site:'apt.puppetlabs.com' isTrusted:True>"])
2016-07-07 16:58:59,398 DEBUG Checking: ruby2.0 (["<Origin component:'main' archive:'precise' origin:'LP-PPA-brightbox-ruby-ng' label:'Brightbox Ruby NG' site:'ppa.launchpad.net' isTrusted:True>"])
2016-07-07 16:58:59,398 DEBUG Checking: ruby2.0-dev (["<Origin component:'main' archive:'precise' origin:'LP-PPA-brightbox-ruby-ng' label:'Brightbox Ruby NG' site:'ppa.launchpad.net' isTrusted:True>"])
2016-07-07 16:58:59,466 DEBUG pkgs that look like they should be upgraded:
2016-07-07 16:58:59,473 DEBUG blacklist: []
2016-07-07 16:58:59,474 DEBUG InstCount=0 DelCount=0 BrokenCout=0
2016-07-07 16:58:59,474 INFO Option --dry-run given, *not* performing real actions
2016-07-07 16:58:59,474 INFO Packages that are upgraded: