i have been trying to upgrade to 15.10 from 14.04 lts and it says error some atuhenticate packages . please i need help . i thought deleting them would help but it didnt

[Warsame Ali]

Description: Ubuntu 14.04.3 LTS
Release: 14.04

N: Unable to locate package pkgname

i wanted to upgrade to 15.10

it says error cant authencate some packages

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.8
ProcVersionSignature: Ubuntu 3.19.0-46.52~14.04.1-generic 3.19.8-ckt12
Uname: Linux 3.19.0-46-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Sat Jan 16 23:14:40 2016
InstallationDate: Installed on 2015-09-02 (136 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-01-17 (0 days ago)
mtime.conffile..etc.update.manager.release.upgrades: 2016-01-16T21:36:30.658467

[Brian Murray (brian-murray)]

The error message from Mainlog.txt follows:

85 2016-01-16 23:04:33,325 DEBUG plugins for condition 'from_trustyPostDistUpgradeCache' are '[]'
 86 2016-01-16 23:04:33,326 DEBUG none of the '['ubuntu-desktop', 'kubuntu-desktop', 'xubuntu-core', 'xubuntu-desktop', 'ubuntustudio-desktop', 'mythbuntu-deskto p', 'kubuntu-netbook', 'lubuntu-core', 'lubuntu-desktop', 'ubuntu-gnome-desktop']' meta-pkgs installed
 87 2016-01-16 23:04:33,326 DEBUG guessing 'ubuntu-desktop' as missing meta-pkg
 88 2016-01-16 23:04:35,380 ERROR failed to mark 'ubuntu-desktop' for install (E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.)
 89 2016-01-16 23:04:35,608 DEBUG blacklist expr 'unity$' matches 'unity'
 90 2016-01-16 23:04:35,608 DEBUG The package 'unity' is marked for removal but it's in the removal blacklist

Please install one of the meta-pkgs for the upgrade to be calculated successfully. You probably want ubuntu-desktop.

[Brian Murray (brian-murray)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1534374, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.