can't upgrade from 14.04 to 15.04

[Jedabero]

Comprobando el gestor de paquetes
Leyendo lista de paquetes... Finalizado
Creando árbol de dependencias
Leyendo la información de estado... Finalizado
Generando estructuras de datos... Finalizado

Calculando los cambios

Calculando los cambios

No se ha podido calcular la actualización

Ha ocurrido un problema mientras se calculaba la actualización.

Eso se ha podido causar por:
* Actualizar a una versión de Ubuntu aún no publicada
* Estar ejecutando la versión actual, aún no publicada, de Ubuntu
* Paquetes no oficiales de software no proporcionados por Ubuntu

Si nada de esto aplica, informe de este error usando la orden
«ubuntu-bug ubuntu-release-upgrader-core» en una terminal.

Would be nice if one could get more output about what's not allowing me to upgrade

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 x86_64
NonfreeKernelModules: wl
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: XFCE
Date: Fri Jan 15 13:32:26 2016
InstallationDate: Installed on 2014-11-21 (420 days ago)
InstallationMedia: Xubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140723)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-01-15 (0 days ago)
mtime.conffile..etc.update.manager.release.upgrades: 2016-01-15T12:47:36.406804

[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.