install ubuntu 18.04.1 by usb - echec de configuration apt

[ujmo4612]

While installation by usb is just running, this message occurs :
in French : "Echec de configuration de l'outil de gestion de paquets (APT)"
"Une tentative de configuration d(APT pour installer de nouveaux paquets depuis le CD (ici USB) a échoué"
when I Valid the installation crashes.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14.6
ProcVersionSignature: Ubuntu 4.15.0-29.31-generic 4.15.18
Uname: Linux 4.15.0-29-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
CasperVersion: 1.394
Date: Sat Sep 15 11:45:01 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
LiveMediaBuild: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Alain Richard (alainrich280356)]

I have to reboot tu make the error 10 dissapear (i hope), refresh the partition table, and make a fresh install