Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/awn/extras/awnlib.py", line 1233, in callback_wrapper
    callback()
  File "/usr/share/avant-window-navigator/applets/battery/battery.py", line 208, in check_status_cb
    charge_percentage = self.backend.get_capacity_percentage()
  File "/usr/share/avant-window-navigator/applets/battery/battery.py", line 428, in get_capacity_percentage
    return int(UPowerBackend.__get_property(self.__battery, "Percentage"))
  File "/usr/share/avant-window-navigator/applets/battery/battery.py", line 398, in __get_property
    return interface.Get(UPowerBackend.device_iface_name, property_name)
  File "/usr/lib/pymodules/python2.7/dbus/proxies.py", line 140, in __call__
    **keywords)
  File "/usr/lib/pymodules/python2.7/dbus/connection.py", line 630, in call_blocking
    message, timeout)
DBusException: org.freedesktop.DBus.Error.UnknownMethod: Method "Get" with signature "ss" on interface "org.freedesktop.DBus.Properties" doesn't exist