[Bug 1519463] Re: Cannot upgrade from Ubuntu 14.04 to 16.04

[Martin BLANCHARD]

Hello, French version : 
"Impossible d'évaluer la mise à niveau

Un problème insoluble est survenu lors de la préparation de la mise à
niveau.

 Ceci peut-être dû à :
 * la mise à niveau vers une version de développement d'Ubuntu ;
 * la version de développement d'Ubuntu est actuellement utilisée ;
 * des paquets logiciels non officiels, non fournis par Ubuntu.

Si rien de tout cela ne s'applique, veuillez signaler ce bogue en
utilisant la commande « ubuntu-bug ubuntu-release-upgrader-core » dans
un terminal."

I am on a Dell XPS 13 (2015) 9343 with Dell installed version of Ubuntu 14.04 (upgraded to 14.04.5) is that can be a source of the bug?
I don't not what to do to fix and upgrade to 16.04

** Attachment added: "screenshot"
   https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/+bug/1519463/+attachment/4826403/+files/Capture%20du%202017-02-25%2009%3A46%3A37.png

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https://bugs.launchpad.net/bugs/1519463

Title:
  Cannot upgrade from Ubuntu 14.04 to 16.04

Status in ubuntu-release-upgrader package in Ubuntu:
  Confirmed

Bug description:
  Russian text:
  Обнаружена неразрешимая проблема при расчёте обновления.

   Это может быть вызвано тем, что:
   * Обновление до пре-релиза Ubuntu
   * Использование текущей пре-релиз версии Ubuntu
   * Неофициальное ПО, не предоставляемое Ubuntu

  Если ничего из перечисленного не подходит, сообщите об этой ошибке,
  выполнив команду «ubuntu-bug ubuntu-release-upgrader-core» в
  терминале.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: ubuntu-release-upgrader-core 1:0.220.8
  ProcVersionSignature: Ubuntu 3.16.0-53.72~14.04.1-generic 3.16.7-ckt18
  Uname: Linux 3.16.0-53-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.19
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: Unity
  Date: Tue Nov 24 22:48:14 2015
  InstallationDate: Installed on 2015-07-24 (123 days ago)
  InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to trusty on 2015-11-24 (0 days ago)
  VarLogDistupgradeTermlog:

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