update from 14.04 to 15.04

[Guillermo]

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

-------------------------------------------------------------------------------------------------------------------
Could not calculate the update

A problem while the update is calculated has occurred.

  That has been caused by:
  * Upgrade to a version of Ubuntu yet published
  * Be running the current version, not yet published, Ubuntu
  * Unofficial software packages not provided by Ubuntu

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.8
ProcVersionSignature: Ubuntu 3.13.0-68.111-generic 3.13.11-ckt27
Uname: Linux 3.13.0-68-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
CrashDB: ubuntu
Date: Thu Nov 19 11:15:04 2015
InstallationDate: Installed on 2014-09-29 (415 days ago)
InstallationMedia:

PackageArchitecture: all
ProcEnviron:
 LANGUAGE=es_AR:es
 TERM=xterm
 PATH=(custom, no user)
 LANG=es_AR.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2015-11-19 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update.manager.release.upgrades: 2015-11-18T12:40:20.767736

[Ubuntu Foundations Team Bug Bot (crichton)]

Reviewing the files from your upgrade attempt you seem to have enabled the xorg-edgers-ppa. This will prevent the upgrade as that PPA contains different versions of packages essential to Ubuntu. The page, https://launchpad.net/~xorg-edgers/+archive/ppa, contains details on to how to revert to the official Xorg packages. Thanks.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[Ubuntu Foundations Team Bug Bot (crichton)]

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 1069133, 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.
[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]