[Kubuntu 15.04 beta] Failed to format ext4 partition in the installation

Kubuntu 15.04 64 bits (Vivid Vervet) from daily build 08/04/2015.

$ lsb_release -rd
Description: Ubuntu Vivid Vervet (development branch)
Release: 15.04

$ apt-cache policy ubiquity
ubiquity:
  Instalados: (ninguno)
  Candidato: 2.21.18
  Tabla de versión:
     2.21.18 0
        500 http://ar.archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages
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Disk /dev/sda: 149,1 GiB, 160041885696 bytes, 312581808 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: 0xf069f069

Device Boot Start End Sectors Size Id Type
/dev/sda1 * 63 20547134 20547072 9,8G 7 HPFS/NTFS/exFAT
/dev/sda2 20547584 61431807 40884224 19,5G 83 Linux
/dev/sda3 61432684 312576704 251144021 119,8G f W95 Ext'd (LBA)
/dev/sda5 61432686 110983167 49550482 23,6G 83 Linux
/dev/sda6 110985216 125386751 14401536 6,9G 83 Linux
/dev/sda7 125387388 188313929 62926542 30G 83 Linux
/dev/sda8 188313993 284784254 96470262 46G b W95 FAT32
/dev/sda9 284784318 302295104 17510787 8,4G 7 HPFS/NTFS/exFAT
/dev/sda10 302295168 306388991 4093824 2G 7 HPFS/NTFS/exFAT
/dev/sda11 306391743 312576704 6184962 3G 82 Linux swap / Solaris
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The partition in question is "sda2".

"sda2" previously existed and had data on it. I had selected Kubuntu manual disk installation as usual, and I chose formatted "sda2" as ext4 and mount as "/". When it began installing it remained static at 33% without progress. Then I tried from KDE "partitionmanager" from the LiveDVD and trying to delete and format "sda2" as ext4 and it also failed with the following message:
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KDE Partition Manager: SMART Status Report
Date: 4/12/15 7:41 PM
Program version: 1.2.1
Backend: pmlibpartedbackendplugin (1)
KDE Frameworks version: 5.7.0
Machine: Linux kubuntu 3.19.0-12-generic #12-Ubuntu SMP Fri Apr 3 04:03:26 UTC 2015 x86_64

Delete partition ‘/dev/sda2’ (19.50 GiB, unknown)
Job: Delete file system on ‘/dev/sda2’
Delete file system on ‘/dev/sda2’: Success
Job: Delete the partition ‘/dev/sda2’
Delete the partition ‘/dev/sda2’: Success
Delete partition ‘/dev/sda2’ (19.50 GiB, unknown): Success
Create a new partition (19.50 GiB, ext4) on ‘/dev/sda’
Job: Create new partition on device ‘/dev/sda’
Create new partition ‘/dev/sda2’: Success
Job: Create file system ‘ext4’ on partition ‘/dev/sda2’
Command: mkfs.ext4 -q /dev/sda2

Proceed anyway? (y,n)

Create file system ‘ext4’ on partition ‘/dev/sda2’: Error
Create a new partition (19.50 GiB, ext4) on ‘/dev/sda’: Error
==
So I entered to my 14.04 installation, and I could delete and format "sda2" as ext4 from GParted. After this the Kubuntu 15.04 installation was successful only selecting "sda2" as "/" without format the partition.