ubuquity crashes in 15.10

[SoloTurn]

i boot ubuntu-15.10 current (2015-10-04) from usb drive. then i attach a external drive with 4 partitions and want to install the same ubuntu on 3 partitions, one is /, one /home, one swap. the disk has a 4th partition as well. for the boot loader i chose the same drive.

i start ubuquity from terminal where i become root first:
sudo su -
ubiquity gtk_ui

ubuquity asks me the partions to use, then location, then account. after that a small window is coming for a second and ubiquity crashes. consistently since weeks.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: ubiquity 2.21.33
ProcVersionSignature: Ubuntu 3.8.0-9.18-generic 3.8.1
Uname: Linux 3.8.0-9-generic i686
ApportVersion: 2.19-0ubuntu1
Architecture: i386
Date: Sun Oct 4 21:32:18 2015
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: Upgraded to wily on 2015-09-13 (20 days ago)

[SoloTurn (soloturn)]

now i tried different and put an ubuntu lts-14.04 LTS on the 4th partition from windows, pendrive, i.e. an iso. i then booted this ubuntu LTS and wanted to install ubuntu on the other 3 partitions, as above. now the installer says (i cannot copy the text unfortunately ...):

failed to unmount partitions
the installer needs to commit changes to the partition tables, but cannot do so because partitions on the following mount points could not be unmounted:
/cdrom

there the installer is right, because i booted from there. but i am wondering why the installer wants to commit anything if i do not change a single one of the partitions.

root@ubuntu:~# lsof /cdrom
lsof: WARNING: can't stat() fuse.gvfsd-fuse file system /run/user/999/gvfs
      Output information may be incomplete.
root@ubuntu:~# mount | grep cdrom
/dev/sdb1 on /cdrom type vfat (ro,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)

[SoloTurn (soloturn)]

not sure if this is not the same than #313452 supposedly fixed years ago ?

[SoloTurn (soloturn)]

bug313452 i mean

[Bougron (francis-bougron)]

This still exits in 16.04 and it is impossible to install the EFI repertory in /EFI of this partition. However it is possible to use another partition. butn after finish the installation, it is not possible to copy on these partition because
ubuntu@ubuntu:/$ ls /cdrom
ubuntu@ubuntu:/$ sudo mount -v /dev/sda1 /mnt/A
mount: /dev/sda1 is already mounted or /mnt/A busy
ubuntu@ubuntu:/$ ls /mnt/A
ubuntu@ubuntu:/$ fuser /dev/sda1
ubuntu@ubuntu:/$

For me, this solution is not good
See. http://www.hostingpics.net/viewer.php?id=449892Screenshotfrom20160521124220.png

PS: I use also a USB drive to install ubuntu.
On EFI, i have a big problem: It is necessary to replace /EFI/BOOT/bootx64.efi by /EFI/ubuntu/grubx64.efi for booting with an external drive. So i use windows10 to do this!