cannot upgrade from 14.04 to 16.04

[mark]

Could not determine the upgrade

An unresolvable problem occurred while calculating the upgrade.

 This can be caused by:
 * Upgrading to a pre-release version of Ubuntu
 * Running the current pre-release version of Ubuntu
 * Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

lsb_release -rd' ubuntu 14.04 LTS

apt-cache policy pkgname

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.9
ProcVersionSignature: Ubuntu 3.13.0-105.152-generic 3.13.11-ckt39
Uname: Linux 3.13.0-105-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
CurrentDmesg.txt:
 [ 41.264543] init: plymouth-stop pre-start process (1617) terminated with status 1
 [ 46.800496] audit_printk_skb: 153 callbacks suppressed
 [ 46.800499] type=1400 audit(1481204958.669:72): apparmor="STATUS" operation="profile_replace" profile="unconfined" name="/usr/lib/cups/backend/cups-pdf" pid=1744 comm="apparmor_parser"
 [ 46.800504] type=1400 audit(1481204958.669:73): apparmor="STATUS" operation="profile_replace" profile="unconfined" name="/usr/sbin/cupsd" pid=1744 comm="apparmor_parser"
 [ 46.800905] type=1400 audit(1481204958.673:74): apparmor="STATUS" operation="profile_replace" profile="unconfined" name="/usr/sbin/cupsd" pid=1744 comm="apparmor_parser"
Date: Thu Dec 8 14:25:23 2016
InstallationDate: Installed on 2013-06-11 (1276 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-12-08 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update.manager.release.upgrades: 2016-12-08T14:21:01.383322

[Seth Arnold (seth-arnold)]

Thanks for taking the time to report this bug and helping to make Ubuntu better. We appreciate the difficulties you are facing, but this appears to be a "regular" (non-security) bug. I have unmarked it as a security issue since this bug does not show evidence of allowing attackers to cross privilege boundaries nor directly cause loss of data/privacy. Please feel free to report any other bugs you may find.