sudo software-properties-gtk
[sudo] password for callous:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/dbus/bus.py", line 177, in activate_name_owner
    return self.get_name_owner(bus_name)
  File "/usr/lib/python3/dist-packages/dbus/bus.py", line 363, in get_name_owner
    's', (bus_name,), **keywords)
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 653, in call_blocking
    message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NameHasNoOwner: Could not get owner of name 'com.ubuntu.SoftwareProperties': no such name

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/software-properties-gtk", line 100, in <module>
    app = SoftwarePropertiesGtk(datadir=options.data_dir, options=options, file=file)
  File "/usr/lib/python3/dist-packages/softwareproperties/gtk/SoftwarePropertiesGtk.py", line 161, in __init__
    proxy = bus.get_object("com.ubuntu.SoftwareProperties", "/")
  File "/usr/lib/python3/dist-packages/dbus/bus.py", line 243, in get_object
    follow_name_owner_changes=follow_name_owner_changes)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 250, in __init__
    self._named_service = conn.activate_name_owner(bus_name)
  File "/usr/lib/python3/dist-packages/dbus/bus.py", line 182, in activate_name_owner
    self.start_service_by_name(bus_name)
  File "/usr/lib/python3/dist-packages/dbus/bus.py", line 280, in start_service_by_name
    'su', (bus_name, flags)))
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 653, in call_blocking
    message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.Spawn.ExecFailed: Cannot launch daemon, file not found or permissions invalid