grub-install fails for Kubuntu 16.04 on RAID 1

[Twisted Lucidity]

Trying to install Kubuntu 16.04 on a desktop which uses RAID 1.

The install starts OK and then fails about half way through with:

Executing 'grub-install /dev/sda' failed.
This is a fatal error.

This, unfortunately, renders it impossible to install Kubuntu.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CasperVersion: 1.376
CurrentDesktop: KDE
Date: Fri May 13 13:09:15 2016
InstallCmdLine: BOOT_IMAGE=(loop)/casper/vmlinuz.efi root=UUID=E1F5-1DE6 file=/cdrom/preseed/kubuntu.seed maybe-ubiquity debian-installer/language=en keyboard-configuration/layoutcode=gb iso-scan/filename=/kubuntu-16.04-desktop-amd64.iso boot=casper noprompt quiet splash --
LiveMediaBuild: Kubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Twisted Lucidity (lucidlytwisted)]

I found that this answer provided enough information to perform the install.
http://askubuntu.com/questions/505446/how-to-install-ubuntu-14-04-with-raid-1-using-desktop-installer

I guess that downgrades this to a feature request.