preseeding partman fails with "no root filesystem" if previous lvm is present

[Ralf Spenneberg]

I am trying to preseed an Ubuntu LTS 12.04 installation without using LVM.
This works fine if a previous linux installation on the same system did not use LVM.
If lvm volumes are already present on the system the preseeding partman fails and "no root filesystem selected" is displayed on the screen. Purging the MBR and rebooting the preseed installation succeeds.
My recipe:

d-i partman-auto/disk string /dev/sda
d-i partman-auto/method string regular
d-i partman-auto/purge_lvm_from_device boolean true
d-i partman-partitioning/confirm_write_new_label boolean true
d-i partman-md/device_remove_md boolean true
d-i partman-lvm/device_remove_lvm boolean true
d-i partman-lvm/confirm boolean true
d-i partman-lvm/confirm_nooverwrite boolean true
d-i partman/confirm_nooverwrite boolean true

d-i partman-auto/expert_recipe string \
      boot-root :: \
              512 50 512 ext3 \
                      $primary{ } $bootable{ } \
                      method{ format } format{ } \
                      use_filesystem{ } filesystem{ ext3 } \
                      mountpoint{ /boot } \
              . \
              500 10000 20000 ext4 \
                      method{ format } format{ } \
                      use_filesystem{ } filesystem{ ext4 } \
                      mountpoint{ / } \
              . \
              64 512 300% linux-swap \
                      method{ swap } format{ } \
              . \
              500 10000 2000000000 ext4 \
              .

# method{ format } format{ } \
# use_filesystem{ } filesystem{ ext4 } \
# mountpoint{ /keep } \

# This makes partman automatically partition without confirmation, provided
# that you told it what to do using one of the methods above.
d-i partman/confirm_write_new_label boolean true
d-i partman-partitioning/confirm_write_new_label boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true
d-i partman/confirm_nooverwrite boolean true
d-i partman/confirm_write_new_label boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true
d-i partman/mount_style select uuid

This is very annoying because unattended installations are not really possible.