Impossible d'utiliser apt-get pour installer en raison d'une erreur avec apport

Je travaille sur un PC Windows 7 avec une boîte virtuelle Xubuntu (Ubuntu 14.04.2 LTS, 64 bits). Dernièrement, j'ai eu des problèmes avec la commande 'apt-get' et avec le Software Updater. Le Software Updater ne peut pas télécharger une des mises à jour - j'ai apporté 2.14.1-0ubuntu3.10 et il essaie d'installer 2.14.1-0ubuntu3.11, mais il échoue.

De plus, lorsque je tape une commande 'apt-get' ou 'dpkg', comme 'apt-get upgrade', j'obtiens des erreurs comme celles qui suivent.

Reading package lists...
Building 
dependency tree...
Reading state information...
The following packages will be upgraded:
  apport
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
2 not fully installed or removed.
Need to get 0 B/180 kB of archives.
After this operation, 20.5 kB of additional disk space will be used.
Do you want to continue? [Y/n] (Reading database ... 314480 files and directories currently installed.)
Preparing to unpack .../apport_2.14.1-0ubuntu3.11_all.deb ...
initctl: Unknown job: apport
  File "/usr/bin/pyclean", line 63
    except (IOError, OSError), e:
                             ^
SyntaxError: invalid syntax
dpkg: warning: subprocess old pre-removal script returned error exit status 1
dpkg: trying script from the new package instead ...
initctl: Unknown job: apport
  File "/usr/bin/pyclean", line 63
    except (IOError, OSError), e:
                             ^
SyntaxError: invalid syntax
dpkg: error processing archive /var/cache/apt/archives/apport_2.14.1-0ubuntu3.11_all.deb (--unpack):
 subprocess new pre-removal script returned error exit status 1
Traceback (most recent call last):
  File "/usr/bin/pycompile", line 35, in <module>
    from debpython.version import SUPPORTED, debsorted, vrepr, \
  File "/usr/share/python/debpython/version.py", line 24, in <module>
    from ConfigParser import SafeConfigParser
ImportError: No module named 'ConfigParser'
dpkg: error while cleaning up:
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 /var/cache/apt/archives/apport_2.14.1-0ubuntu3.11_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)