problem during upgrade from ubuntu 14.04 to ubutntu 15.10

[Battant]

Hello,

I had the following recurrent problems during upgrade from ubuntu 14.04 LTS 64 bi to ubutntu 15.10

steps to reproduce the bug :
ubuntu settings
1. go to the system settings.
2. Click software update
3. On the update tab make sure you have selected
4. notify me of a new ubuntu version is set to "for any new version"

Steps to reproduce
1. "go to software update and start the upgrade process"
2. problem : . when the download process is finished during the install process, the user session is locked so you see the login screen
3. When you try to enter your password and press return your valid password is not recognized so the scream turn to black and the login screen is show again.
- you can try again and again and again.
--> to exit this infinity loop, I have restarted my laptop without any device connected
--> so I can work only I the terminal and when I try to install any package I see the package database is brocken

So my workaround was :
1. take another computer to create an ubuntu 15.10 64 bit dvd
2. Start the ubuntu computer with the dvd
3. select install
4- At the install option screen select the first option. "reinstalll ubuntu"

Question
Could you fix this bug to allow the automatic upgrade work successfully ?

Best regards

Battant
---
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
CurrentDesktop: Unity
DistroRelease: Ubuntu 14.04
InstallationDate: Installed on 2015-10-01 (195 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
Package: init-system-helpers 1.14
PackageArchitecture: all
ProcVersionSignature: Ubuntu 3.13.0-85.129-generic 3.13.11-ckt36
Tags: third-party-packages trusty
Uname: Linux 3.13.0-85-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
_MarkForUpload: True

[Battant (mparchet)]

apport information

[Battant (mparchet)]

apport information