private final void removeResourceGroups(AuthzSubject subject, Collection<ResourceGroup> groups) {
   for (ResourceGroup group : groups) {
     try {
       resourceGroupManager.removeResourceGroup(subject, group.getId());
     } catch (Exception e) {
       log.error("Unable to remove group: " + e, e);
     }
   }
   if (log.isDebugEnabled()) {
     log.debug("Removed " + groups.size() + " resource groups");
   }
 }