Comment 6 for bug 1426436

Procedure to reproduce for me:-

Note I used easy2boot as this compaq mini 700 is not happy booting directly it seems.
Don't get the opportunity (due to gfxboot.c32: not a com32R image even if live-installer boot option used) to add the following:-
removed quiet splash and put in nomodeset acpi_os_name=Linux via F6 option on boot screen

English
Download updates & 3rd party stuff
(long pause here)
something else
used existing vg and lvs
xfs format / (on lv)
swap area (on lv)
sda1 ext2 /boot
left device for booting installation at “/dev/sda”
login auto
When it got to the “Installing ‘grub2’ package…”
Dialog
“The ‘grub-pc’ package failed to install into /target/. Without the GRUB boot loader, the installed system will not boot.”
OK = only option.
Bootloader install failed (as superuser)
chose the same device ie /dev/sda
Then both the installation is complete dialog and a repeat of the Sorry, an error occurred and it was not possible to install the bootloader.

N.B. in syslog we have:-

Ubiquity: Package grub-pc is not available, but is referred to by another package.
However the following packages replace it: grub-common

E: Package ‘grub-pc’ has no installation candidate
grub-installer: info : Calling ‘apt-install grub-pc’ failed

Hope that helps (MD5 checked and is:- d74b2ca893e227f2063804db627d98c5
ie 3/3/2015 32bit version.
also note that apt-get install grub-common shows grub-common as installed.

On trying to install grub-pc I got an error that a repository couldn't be reached (seemed to be via ipv6 address), downed and upped eth0 and was then able to find and install grub-pc but I had problems configuring grub-pc.
Could this be an ipv6 issue as seems rare and I am on a pretty bizarre network (at least double natted)