return empty list when there are no service dependencies
diff --git a/xos/core/xoslib/methods/vtn.py b/xos/core/xoslib/methods/vtn.py
index 1a2af53..c9dbf3a 100644
--- a/xos/core/xoslib/methods/vtn.py
+++ b/xos/core/xoslib/methods/vtn.py
@@ -57,7 +57,8 @@
         for xos_service in Service.objects.all():
             if service in xos_service.get_vtn_src_ids():
                 return Response(xos_service.get_vtn_dependencies_ids())
-        raise DoesNotExist()
+        return Response([])
+        # raise DoesNotExist()
 
     def list(self, request):
         raise Exception("Not Implemented")