[vivid regression] automatic LVM+encrypted partitioning fails -- needs merging LVM

Medium: vivid amd64 daily from 20141116
Installation target: QEMU (vivid host), virtio, 12 GB virtual disk

In the partitioning screen I merely enabled "encrypt disks", which (rightfully) auto-enabled LVM. After continuing I got an error message that partitioning failed.

/dev/mapper/vda5_crypt -> /dev/dm-0 was created, but no LVs:

$ sudo pvdisplay
  --- Physical volume ---
  PV Name /dev/mapper/vda5_crypt
  VG Name ubuntu-vg
  PV Size 11.76 GiB / not usable 4.00 MiB
  Allocatable yes
  PE Size 4.00 MiB
  Total PE 3009
  Free PE 3009
  Allocated PE 0
  PV UUID OxY3I1-8kGQ-MQP6-c7GX-91PJ-f6sj-pYtRkQ

$ sudo vgdisplay
  --- Volume group ---
  VG Name ubuntu-vg
  System ID
  Format lvm2
  Metadata Areas 1
  Metadata Sequence No 1
  VG Access read/write
  VG Status resizable
  MAX LV 0
  Cur LV 0
  Open LV 0
  Max PV 0
  Cur PV 1
  Act PV 1
  VG Size 11.75 GiB
  PE Size 4.00 MiB
  Total PE 3009
  Alloc PE / Size 0 / 0
  Free PE / Size 3009 / 11.75 GiB
  VG UUID hHorMb-Zl2T-zi2f-IeF2-vwyU-2fKY-apqFDQ

$ sudo lvdisplay
# (empty)

$ sudo fdisk -l /dev/vda

Disk /dev/vda: 12 GiB, 12884901888 bytes, 25165824 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x7d4b553b

Device Boot Start End Sectors Size Id Type
/dev/vda1 2048 499711 497664 243M 83 Linux
/dev/vda2 501758 25163775 24662018 11.8G 5 Extended
/dev/vda5 501760 25163775 24662016 11.8G 83 Linux

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: ubiquity 2.21.0
ProcVersionSignature: Ubuntu 3.16.0-24.32-generic 3.16.4
Uname: Linux 3.16.0-24-generic x86_64
ApportVersion: 2.14.7-0ubuntu10
Architecture: amd64
CasperVersion: 1.346
CurrentDesktop: Unity
Date: Mon Nov 17 09:18:54 2014
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash --
LiveMediaBuild: Ubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20141116)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)