Comment 1 for bug 1404188

Looks like an app armour thing.

Debug-helper> Executing /usr/bin/qmlscene['/usr/bin/qmlscene', '$@', 'share/qml/nmsessiontest/nmsessiontest.qml']
process 7885: arguments to dbus_message_new_method_call() were incorrect, assertion "_dbus_check_is_valid_path (path)" failed in file ../../dbus/dbus-message.c line 1344.
This is normally a bug in some application using the D-Bus library.
process 7885: arguments to dbus_message_set_auto_start() were incorrect, assertion "message != NULL" failed in file ../../dbus/dbus-message.c line 3029.
This is normally a bug in some application using the D-Bus library.
process 7885: arguments to dbus_message_iter_init_append() were incorrect, assertion "message != NULL" failed in file ../../dbus/dbus-message.c line 2426.
This is normally a bug in some application using the D-Bus library.
QDBusConnection: error: could not send message to service "org.freedesktop.NetworkManager" path "" interface "org.freedesktop.DBus.Introspectable" member "Introspect":
using blocking call!
Using blocking call!
process 7885: arguments to dbus_message_new_method_call() were incorrect, assertion "_dbus_check_is_valid_path (path)" failed in file ../../dbus/dbus-message.c line 1344.
This is normally a bug in some application using the D-Bus library.
process 7885: arguments to dbus_message_set_auto_start() were incorrect, assertion "message != NULL" failed in file ../../dbus/dbus-message.c line 3029.
This is normally a bug in some application using the D-Bus library.
process 7885: arguments to dbus_message_iter_init_append() were incorrect, assertion "message != NULL" failed in file ../../dbus/dbus-message.c line 2426.
This is normally a bug in some application using the D-Bus library.
QDBusConnection: error: could not send message to service "org.freedesktop.NetworkManager" path "" interface "org.freedesktop.DBus.Introspectable" member "Introspect":
using blocking call!
Using blocking call!
UbuntuWindow::handleSurfaceFocusChange(focused=true)
UbuntuWindow::handleSurfaceResize(width=540, height=919)
UbuntuClipboard - Got invalid serialized mime data. Ignoring it.

There was another bug mentioning that abstract dbus interface does not introspect, whereas QDBusInterface does
QDBusInterface is used all over in the nm QtBearer plugin.