Otherwise, if the service is not available, we get things like:
===============================================================================
[ERROR]: tests.test_preferences.PreferencesTests.test_login_check
Traceback (most recent call last):
Failure: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.UnknownMethod: Traceback (most recent call last):
File "/usr/lib/pymodules/python2.6/dbus/service.py", line 649, in _message_cb
(candidate_method, parent_method) = _method_lookup(self, method_name, interface_name)
File "/usr/lib/pymodules/python2.6/dbus/service.py", line 244, in _method_lookup
raise UnknownMethodException('%s is not a valid method of interface %s' % (method_name, dbus_interface))
UnknownMethodException: org.freedesktop.DBus.Error.UnknownMethod: Unknown method: login is not a valid method of interface com.ubuntu.sso
This seems to be due to the way DBus interfaces are tested in syncdaemon. The DBusTwistedTestCase is somewhat specific, and always provides the syncdaemon dbus api. When the test is created, the interface name is changed to com.ubuntu.sso, but the interface hasn't changed, so it doesn't provide the required login method, and we get the error above.
The DBusTestCase in ubuntuone.