$ gnome-settings-daemon -r

** (gnome-settings-daemon:19028): WARNING **: You can only run one xsettings manager at a time; exiting

** (gnome-settings-daemon:19028): WARNING **: Unable to start gnome_xsettings manager: Could not initialize xsettings manager.

(gnome-settings-daemon:19028): clipboard-plugin-WARNING **: Clipboard manager is already running.

(gnome-settings-daemon:19028): GLib-GObject-WARNING **: cannot register existing type 'GsdDeviceManager'

(gnome-settings-daemon:19028): GLib-CRITICAL **: g_once_init_leave: assertion 'result != 0' failed

(gnome-settings-daemon:19028): common-plugin-CRITICAL **: gsd_device_manager_list_devices: assertion 'GSD_IS_DEVICE_MANAGER (manager)' failed

(gnome-settings-daemon:19028): color-plugin-WARNING **: failed to create device: could not check org.freedesktop.color-manager.create-device for auth: GDBus.Error:org.freedesktop.PolicyKit1.Error.NotAuthorized: Only trusted callers (e.g. uid 0 or an action owner) can use CheckAuthorization() for subjects belonging to other identities


Additional output with "--debug" parameter:
** (gnome-settings-daemon:19571): DEBUG: Loading plugin: /usr/lib/gnome-settings-daemon-3.0/media-keys.gnome-settings-plugin
** (gnome-settings-daemon:19571): DEBUG: GnomeSettingsPluginInfo: name='Medientasten' file='/usr/lib/gnome-settings-daemon-3.0/media-keys.gnome-settings-plugin' location='media-keys'
[SNIP]
** (gnome-settings-daemon:19571): DEBUG: GnomeSettingsModule 0xa935e0 initialising
** (gnome-settings-daemon:19571): DEBUG: Loading /usr/lib/gnome-settings-daemon-3.0/libmedia-keys.so
** (gnome-settings-daemon:19571): DEBUG: Creating object of type GsdMediaKeysPlugin
(gnome-settings-daemon:19571): media-keys-plugin-DEBUG: GsdMediaKeys initializing
(gnome-settings-daemon:19571): media-keys-plugin-DEBUG: Adding system inhibitors for power keys
(gnome-settings-daemon:19571): media-keys-plugin-DEBUG: Activating gsd_media_keys plugin
** (gnome-settings-daemon:19571): DEBUG: GnomeSettingsManager: emitting plugin-activated media-keys
** (gnome-settings-daemon:19571): DEBUG: Plugin media-keys: active
