update manager does not start anymore

I have 14.04 LTS on the system.
Now update manager will not start from the dash nor with sudo update-manager.
I followed some suggestions from previous questions as:
sudo apt-get install --reinstall python3-distupgrade and in the end it says:

 from xml.parsers.expat import ParserCreate
ImportError: No module named 'xml.parsers'
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in apport_excepthook
    from apport.fileutils import likely_packaged, get_recent_crashes
  File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in <module>
    from apport.report import Report
  File "/usr/lib/python3/dist-packages/apport/report.py", line 15, in <module>
    import xml.dom, xml.dom.minidom
ImportError: No module named 'xml.dom'

Original exception was:
Traceback (most recent call last):
  File "/usr/bin/update-manager", line 37, in <module>
    from UpdateManager.UpdateManager import UpdateManager
  File "/usr/lib/python3/dist-packages/UpdateManager/UpdateManager.py", line 43, in <module>
    import dbus
  File "/usr/lib/python3/dist-packages/dbus/__init__.py", line 103, in <module>
    from dbus._dbus import Bus, SystemBus, SessionBus, StarterBus
  File "/usr/lib/python3/dist-packages/dbus/_dbus.py", line 39, in <module>
    from dbus.bus import BusConnection
  File "/usr/lib/python3/dist-packages/dbus/bus.py", line 39, in <module>
    from dbus.connection import Connection
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 37, in <module>
    from dbus.proxies import ProxyObject
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 34, in <module>
    from dbus._expat_introspect_parser import process_introspection_data
  File "/usr/lib/python3/dist-packages/dbus/_expat_introspect_parser.py", line 26, in <module>
    from xml.parsers.expat import ParserCreate
ImportError: No module named 'xml.parsers'

Can somebody help with this problem?