Ubuntu 14.04.2 installer manual partitioning

[Obri]

i'm trying to install Ubuntu 14.04.2 on Power8 Hardware. I'm having some trouble with manually
partitioning the disk, the error occurs on hardware and also with
powerkvm. It could be related to [1]

My Partition layout:

Partition Size Type
sda1 29MB PowerPC PReP
sda2 256MB ext4 /boot
sda3 10G LVM

Volume Group: VG01_mariadb01

Volume Size Type
ROOT 4G ext4 /
VAR 4G ext4 /var
SWAP swap

When i select "Finish partitioning and write changes to disk"

I get this error:

------------------------------------------------------------------------
The file system on /dev/sda1 assigned to / has not been marked for
formatting. Directories containing system files
(/etc, /lib, /usr, /var, ...) that already exist under any defined
mountpoint will be deleted during the install.

Please ensure that you have backed up any critical data before
installing.

Do you want to return to the partitioner?

<Go Back> <Yes> <No>
------------------------------------------------------------------------

I select No because there is no data on /dev/sda1, /dev/sda1 is the
PReP Partition. After that, i get another error:

-------------------------------------------------------------------------
Failed to delete conflicting files

The installer needs to remove operating system files from the install
target, but was unable to do so. The install cannot continue
-------------------------------------------------------------------------

There is no data on /dev/sda1 i did overwrite all data on it with dd
for one try.

Ubuntu works with automatic partitioning.

If i answer <Go Back> to the Question and then delete and re create the PReP Partition, the installation does work.

[1] https://bugs.launchpad.net/ubuntu/+source/curtin/+bug/1371133

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.