When i am installing Ubuntu 16.04 with Multisystem

[Bougron]

Just before bug The message was
'le paquet grub-efi amd64-signed n'a pas pu être installé dans /target/. En l'absence du programme de démarrage GRUB, le system isntallé ne pourra démarrer"

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic i686
ApportVersion: 2.20.1-0ubuntu2
Architecture: i386
CasperVersion: 1.376
Date: Mon May 9 21:43:03 2016
InstallCmdLine: BOOT_IMAGE=(loop)/casper/vmlinuz root=UUID=E298-7EA1 maybe-ubiquity debian-installer/language=fr keyboard-configuration/layoutcode=fr keyboard-configuration/variantcode=oss iso-scan/filename=/ubuntu-16.04-desktop-i386.iso boot=casper file=/cdrom/preseed/ubuntu.seed noprompt quiet splash --
LiveMediaBuild: Ubuntu 16.04 LTS "Xenial Xerus" - Release i386 (20160420.1)
ProcEnviron:
 LANGUAGE=fr_FR.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_FR.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)