Fix bug 987

Change-Id: I72d490b765d04b00b912fd19002c51580f286da0
Signed-off-by: quilesj <e.nvi001.tid@telefonica.com>
diff --git a/osm_lcm/ns.py b/osm_lcm/ns.py
index f5221d1..2e0ca39 100644
--- a/osm_lcm/ns.py
+++ b/osm_lcm/ns.py
@@ -1112,11 +1112,11 @@
             if vnfr_id:
                 element_type = 'VNF'
                 element_under_configuration = vnfr_id
-                namespace += "." + vnfr_id
+                namespace += ".{}".format(vnfr_id)
                 if vdu_id:
                     namespace += ".{}-{}".format(vdu_id, vdu_index or 0)
                     element_type = 'VDU'
-                    element_under_configuration = vdu_id + '-' + vdu_index
+                    element_under_configuration = "{}-{}".format(vdu_id, vdu_index or 0)
 
             # Get artifact path
             artifact_path = "{}/{}/charms/{}".format(