Installer crashes trying to install grub on mdadm imsm raid1

[John Center]

I had a feeling this would happen, installer only understands dmraid, not mdadm imsm raid.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: ubiquity 2.12.16
ProcVersionSignature: Ubuntu 3.5.0-17.28-generic 3.5.5
Uname: Linux 3.5.0-17-generic x86_64
ApportVersion: 2.6.1-0ubuntu9
Architecture: amd64
CasperVersion: 1.328
Date: Wed Dec 19 18:33:13 2012
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- nodmraid
LiveMediaBuild: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MarkForUpload: True
ProcEnviron:
 TERM=unknown
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)