test_scene_selector_operation failed from mako #76

This test is failing frequently on mako, last seen in image #76. This is the error that is given:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/mediaplayer_app/tests/test_player_with_video.py", line 31, in setUp
    self.launch_app("h264.avi")
  File "/usr/lib/python2.7/dist-packages/mediaplayer_app/tests/__init__.py", line 42, in launch_app
    self.launch_test_installed(movie_file)
  File "/usr/lib/python2.7/dist-packages/mediaplayer_app/tests/__init__.py", line 69, in launch_test_installed
    app_type='qt')
  File "/usr/lib/python2.7/dist-packages/autopilot/testcase.py", line 264, in launch_test_application
    return self._launch_test_application(launcher, application, *arguments)
  File "/usr/lib/python2.7/dist-packages/autopilot/testcase.py", line 367, in _launch_test_application
    application_name=application_name,
  File "/usr/lib/python2.7/dist-packages/autopilot/introspection/__init__.py", line 187, in get_proxy_object_for_existing_process
    return _make_proxy_object(dbus_addresses[0], emulator_base)
  File "/usr/lib/python2.7/dist-packages/autopilot/introspection/__init__.py", line 455, in _make_proxy_object
    intro_xml = _get_introspection_xml_from_backend(data_source)
  File "/usr/lib/python2.7/dist-packages/autopilot/introspection/__init__.py", line 547, in _get_introspection_xml_from_backend
    return backend.dbus_introspection_iface.Introspect()
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 70, in __call__
    return self._proxy_method(*args, **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 651, in call_blocking
    message, timeout)
DBusException: org.freedesktop.DBus.Error.NoReply: Message did not receive a reply (timeout by message bus)

This looks like autopilot was unable to introspect the media player application, perhaps because it didn't start. I haven't been able to reproduce this locally despite many reruns, but it seems to fail frequently in CI so this bug will track it to being fixed (eventually).