issue a warning when get_slivers is used against an existing but empty slice

e.g. with this code one gets an exception when trying to renew an existing slice that has no node
the warning would help spotting this

diff --git a/sfa/planetlab/plaggregate.py b/sfa/planetlab/plaggregate.py
index 9ab8c6d..6fabf79 100644 (file)
--- a/sfa/planetlab/plaggregate.py
+++ b/sfa/planetlab/plaggregate.py
@@ -142,13 +142,18 @@ class PlAggregate:
         if slice_ids:
             filter['slice_id'] = list(slice_ids)
         # get all slices
-        all_slices = self.driver.shell.GetSlices(filter, ['slice_id', 'name', 'hrn', 'person_ids', 'node_ids', 'slice_tag_ids', 'expires'])
+        fields = ['slice_id', 'name', 'hrn', 'person_ids', 'node_ids', 'slice_tag_ids', 'expires']
+        all_slices = self.driver.shell.GetSlices(filter, fields)
         if slice_hrn:
             slices = [slice for slice in all_slices if slice['hrn'] == slice_hrn]
         else:
             slices = all_slices
       
         if not slices:
+            if slice_hrn:
+                logger.error("PlAggregate.get_slivers : no slice found with hrn {}".format(slice_hrn))
+            else:
+                logger.error("PlAggregate.get_slivers : no sliver found with urns {}".format(urns))
             return []
         slice = slices[0]     
         slice['hrn'] = slice_hrn   
@@ -197,6 +202,8 @@ class PlAggregate:
             node['urn'] = node['sliver_id'] 
             node['services_user'] = users
             slivers.append(node)
+        if not slivers:
+            logger.warning("PlAggregate.get_slivers : slice(s) found but with no sliver {}".format(urns))
         return slivers
 
     def node_to_rspec_node(self, node, sites, interfaces, node_tags, pl_initscripts=None, grain=None, options=None):