Arch Linux
networkmanager
Version        : 0.9.8.2-1

When, for instance, the network interface is brought down manually and allowed to come back-up automatically, there is this in the log:

 NetworkManager[225]: <info> Activation (enp2s0) successful, device activated.
 dbus-daemon[229]: dbus[229]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service'
 dbus[229]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service'
 systemd[1]: Got D-Bus request: org.freedesktop.systemd1.Activator.ActivationRequest() on /org/freedesktop/DBus
 systemd[1]: Got D-Bus activation request for dbus-org.freedesktop.nm-dispatcher.service
 systemd[1]: Failed to load configuration for 
dbus-org.freedesktop.nm-dispatcher.service: No such file or directory
 systemd[1]: Trying to enqueue job dbus-org.freedesktop.nm-dispatcher.service/start/replace
 systemd[1]: D-Bus activation failed for dbus-org.freedesktop.nm-dispatcher.service: Invalid argument
 dbus[229]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.nm-dispatcher.service': Unit dbus-org.freedesktop.nm-dispatcher.service failed to load: No such file or directory. See system logs and 'systemctl status dbus-org.freedesktop.nm-dispatcher.service' for details.
 NetworkManager[225]: <warn> Dispatcher failed: (32) Unit 
dbus-org.freedesktop.nm-dispatcher.service failed to load: No such file or 
directory. See system logs and 'systemctl status dbus-org.freedesktop.nm-dispatcher.service' for details.
 dbus-daemon[229]: dbus[229]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.nm-dispatcher.service': Unit dbus-org.freedesktop.nm-dispatcher.service failed to load: No such file or directory. See system logs and 'systemctl status

Other times, there is simply:

 systemd[1]: Running GC...
 systemd[1]: Got D-Bus request: org.freedesktop.DBus.Properties.GetAll() on 
/org/freedesktop/systemd1/unit/dbus_2dorg_2efreedesktop_2enm_2ddispatcher_2eserv
ice
 systemd[1]: Failed to load configuration for 
dbus-org.freedesktop.nm-dispatcher.service: No such file or directory

The file "/usr/lib/systemd/system/NetworkManager-dispatcher.service" has the line:

 Alias=dbus-org.freedesktop.nm-dispatcher.service

but that is probably not needed.

Please see the Modem Manager bug report at
 https://bugzilla.gnome.org/show_bug.cgi?id=701229
for a possibly similar problem and solution.

James