can not upgrade from 14.04 to 15.04

[Lothar]

the upgrade says: can not trusted hud,aqt-get

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.8
ProcVersionSignature: Ubuntu 3.13.0-74.118-generic 3.13.11-ckt30
Uname: Linux 3.13.0-74-generic i686
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: i386
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Fri Jan 8 12:23:32 2016
InstallationDate: Installed on 2016-01-05 (3 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release i386 (20131016.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-01-08 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update.manager.release.upgrades: 2016-01-07T13:26:10.654012

[Brian Murray (brian-murray)]

Please install the ubuntu-desktop meta package and try the upgrade again.

64 2016-01-08 12:22:31,840 DEBUG none of the '['ubuntu-desktop', 'kubuntu-desktop', 'xubuntu-core', 'xubuntu-desktop', 'ubuntustudio-desktop', 'mythbuntu-desktop' , 'kubuntu-netbook', 'lubuntu-core', 'lubuntu-desktop', 'ubuntu-gnome-desktop']' meta-pkgs installed
 65 2016-01-08 12:22:31,841 DEBUG guessing 'ubuntu-desktop' as missing meta-pkg
 66 2016-01-08 12:22:32,334 ERROR failed to mark 'ubuntu-desktop' for install (E:Probleme können nicht korrigiert werden, Sie haben zurückgehaltene defekte Pakete. )
 67 2016-01-08 12:22:45,898 DEBUG blacklist expr 'unity$' matches 'unity'
 68 2016-01-08 12:22:45,898 DEBUG The package 'unity' is marked for removal but it's in the removal blacklist