grub-installer failed while installing Ubuntu GNOME from live

[Takayoshi Mori]

grub-installer failure kept me from installing Ubuntu GNOME from a live USB.
I don't know if this is a real bug. Even if not, it may be annoying because I was able to cause the problem easily with the normal interface.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: ubiquity 2.20.0
ProcVersionSignature: Ubuntu 3.16.0-23.31-generic 3.16.4
Uname: Linux 3.16.0-23-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CasperVersion: 1.345
Date: Tue Jan 20 22:37:45 2015
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu-gnome.seed boot=casper quiet splash --
LiveMediaBuild: Ubuntu-GNOME 14.10 "Utopic Unicorn" - Release amd64 (20141022.1)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)