Fix exception mgmt in async function kubectl.get_generic_object

Change-Id: I98c4759dffbc743cc83f19d492b745a6a94c7f31
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/osm_lcm/n2vc/kubectl.py b/osm_lcm/n2vc/kubectl.py
index a1ac6de..eac857a 100644
--- a/osm_lcm/n2vc/kubectl.py
+++ b/osm_lcm/n2vc/kubectl.py
@@ -883,7 +883,8 @@
         except ApiException as e:
             self.logger.debug(f"Exception: {e}")
             info = json.loads(e.body)
-            raise f"Api Exception: {e}. Reason: {info.get('reason')}"
+            self.logger.debug(f"Api Exception: {e}. Reason: {info.get('reason')}")
+            return None
 
     async def list_generic_object(
         self,