Erreur Python lors de l'ouverture de software-center

Mon centre logiciel ne fonctionne soudainement plus. Lorsque j'ai essayé de l'ouvrir à partir du lanceur, il se charge mais ne montre rien.

J'ai essayé de l'exécuter à partir du terminal, et j'ai obtenu cette erreur :

Traceback (most recent call last):
  File "/usr/bin/software-center", line 36, in <module>
    from softwarecenter.utils import (
  File "/usr/share/software-center/softwarecenter/utils.py", line 19, in <module>
    import dbus
  File "/usr/lib/python2.7/dist-packages/dbus/__init__.py", line 103, in <module>
    from dbus._dbus import Bus, SystemBus, SessionBus, StarterBus
  File "/usr/lib/python2.7/dist-packages/dbus/_dbus.py", line 39, in <module>
    from dbus.bus import BusConnection
  File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 39, in <module>
    from dbus.connection import Connection
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 37, in <module>
    from dbus.proxies import ProxyObject
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 34, in <module>
    from dbus._expat_introspect_parser import process_introspection_data
  File "/usr/lib/python2.7/dist-packages/dbus/_expat_introspect_parser.py", line 26, in <module>
    from xml.parsers.expat import ParserCreate
  File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module>
    from pyexpat import *
ImportError: /usr/lib/python2.7/lib-dynload/pyexpat.x86_64-linux-gnu.so: undefined symbol: XML_SetHashSalt
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 63, in apport_excepthook
    from apport.fileutils import likely_packaged, get_recent_crashes
  File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 5, in <module>
    from apport.report import Report
  File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module>
    from xml.parsers.expat import ExpatError
  File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module>
    from pyexpat import *
ImportError: /usr/lib/python2.7/lib-dynload/pyexpat.x86_64-linux-gnu.so: undefined symbol: XML_SetHashSalt

Original exception was:
Traceback (most recent call last):
  File "/usr/bin/software-center", line 36, in <module>
    from softwarecenter.utils import (
  File "/usr/share/software-center/softwarecenter/utils.py", line 19, in <module>
    import dbus
  File "/usr/lib/python2.7/dist-packages/dbus/__init__.py", line 103, in <module>
    from dbus._dbus import Bus, SystemBus, SessionBus, StarterBus
  File "/usr/lib/python2.7/dist-packages/dbus/_dbus.py", line 39, in <module>
    from dbus.bus import BusConnection
  File "/usr/lib/python2.7/dist-packages/dbus/bus.py", line 39, in <module>
    from dbus.connection import Connection
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 37, in <module>
    from dbus.proxies import ProxyObject
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 34, in <module>
    from dbus._expat_introspect_parser import process_introspection_data
  File "/usr/lib/python2.7/dist-packages/dbus/_expat_introspect_parser.py", line 26, in <module>
    from xml.parsers.expat import ParserCreate
  File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module>
    from pyexpat import *
ImportError: /usr/lib/python2.7/lib-dynload/pyexpat.x86_64-linux-gnu.so: undefined symbol: XML_SetHashSalt

Si je me souviens bien, je ne fais rien avec la bibliothèque Python. J'ai fait quelques recherches sur Google et les gens m'ont dit de faire ce qui suit apt-get update & upgrade . Je les ai essayés, mais sans succès.

アップデイト

J'ai essayé de réinstaller python & software-center en utilisant :

sudo apt-get install --reinstall python2.7
sudo apt-get install --reinstall software-center

Mais l'erreur persiste

Merci pour votre temps.