mise à jour vers ubuntu 18.04 lts impossible liste source

[A]

Si cette page était en français je comprendrais mieux ce que l'on me demande.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.10
ProcVersionSignature: Ubuntu 3.13.0-147.196-generic 3.13.11-ckt39
Uname: Linux 3.13.0-147-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.28
Architecture: amd64
CrashDB: ubuntu
Date: Sat May 19 18:09:21 2018
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-trusty-amd64-20140620-0
InstallationDate: Installed on 2018-03-31 (48 days ago)
InstallationMedia: Ubuntu 14.04 "Trusty" - Build amd64 LIVE Binary 20140620-04:25
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=fr_FR
 PATH=(custom, no user)
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2018-05-19 (0 days ago)
VarLogDistupgradeAptlog:
 Log time: 2018-05-19 17:55:48.820608
 Log time: 2018-05-19 17:56:37.945215
 Log time: 2018-05-19 18:09:00.799228
 Log time: 2018-05-19 18:09:35.838615
VarLogDistupgradeTermlog: