Installer frozen at 61% (configuring grub-common(amd64))

Reproducible: Always

Steps to Reproduce:
1. Start the installer
2. Wait for all the data to download
3. Cry when the installer freezes




TraceBack:
100% [Working]                                                                  QInotifyFileSystemWatcherEngine::addPaths: inotify_add_watch failed: No such file or directory
QFileSystemWatcher: failed to add paths: /root/.config/ibus/bus
Bus::open: Can not get ibus-daemon's address. 
IBusInputContext::createInputContext: no connection to ibus-daemon 
exitMainLoop
Traceback (most recent call last):
  File "/tmp/ubuntu-release-upgrader-6_e044er/vivid", line 8, in <module>
    sys.exit(main())
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeMain.py", line 240, in main
    if app.run():
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeController.py", line 1831, in run
    return self.fullUpgrade()
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeController.py", line 1796, in fullUpgrade
    if not self.doDistUpgrade():
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeController.py", line 1137, in doDistUpgrade
    res = self.cache.commit(fprogress,iprogress)                                                                                                                                                             
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeCache.py", line 267, in commit                                                                                                          
    apt.Cache.commit(self, fprogress, iprogress)                                                                                                                                                             
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 501, in commit                                                                                                                                    
    res = self.install_archives(pm, install_progress)                                                                                                                                                        
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 465, in install_archives                                                                                                                          
    res = install_progress.run(pm)                                                                                                                                                                           
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeView.py", line 234, in run                                                                                                              
    res = os.WEXITSTATUS(self.wait_child())                                                                                                                                                                  
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeViewKDE.py", line 451, in wait_child                                                                                                    
    self.update_interface()                                                                                                                                                                                  
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeViewKDE.py", line 430, in update_interface                                                                                              
    InstallProgress.update_interface(self)                                                                                                                                                                   
  File "/usr/lib/python3/dist-packages/apt/progress/base.py", line 252, in update_interface                                                                                                                  
    self.conffile(match.group(1), match.group(2))                                                                                                                                                            
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeViewKDE.py", line 339, in conffile                                                                                                      
    self.confDialogue.show_difference_button.clicked.connect(self.showConffile())                                                                                                                            
TypeError: connect() slot argument should be a callable or a signal, not 'NoneType'                                                                                                                          
Error in sys.excepthook:                                                                                                                                                                                     
Traceback (most recent call last):                                                                                                                                                                           
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 102, in apport_excepthook
    pr.add_proc_info(extraenv=['PYTHONPATH', 'PYTHONHOME'])
  File "/usr/lib/python3/dist-packages/apport/report.py", line 521, in add_proc_info
    raise ValueError('%s does not exist' % self['ExecutablePath'])
ValueError: /usr/bin/python3.4.dpkg-new (deleted) does not exist

Original exception was:
Traceback (most recent call last):
  File "/tmp/ubuntu-release-upgrader-6_e044er/vivid", line 8, in <module>
    sys.exit(main())
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeMain.py", line 240, in main
    if app.run():
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeController.py", line 1831, in run
    return self.fullUpgrade()
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeController.py", line 1796, in fullUpgrade
    if not self.doDistUpgrade():
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeController.py", line 1137, in doDistUpgrade
    res = self.cache.commit(fprogress,iprogress)
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeCache.py", line 267, in commit
    apt.Cache.commit(self, fprogress, iprogress)
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 501, in commit
    res = self.install_archives(pm, install_progress)
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 465, in install_archives
    res = install_progress.run(pm)
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeView.py", line 234, in run
    res = os.WEXITSTATUS(self.wait_child())
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeViewKDE.py", line 451, in wait_child
    self.update_interface()
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeViewKDE.py", line 430, in update_interface
    InstallProgress.update_interface(self)
  File "/usr/lib/python3/dist-packages/apt/progress/base.py", line 252, in update_interface
    self.conffile(match.group(1), match.group(2))
  File "/tmp/ubuntu-release-upgrader-6_e044er/DistUpgrade/DistUpgradeViewKDE.py", line 339, in conffile
    self.confDialogue.show_difference_button.clicked.connect(self.showConffile())
TypeError: connect() slot argument should be a callable or a signal, not 'NoneType'