/**
  * rollback Zookeeper update.
  *
  * @param env MasterProcedureEnv
  * @throws IOException
  */
 private void rollbackZKNamespaceManagerChange(final MasterProcedureEnv env) throws IOException {
   try {
     DeleteNamespaceProcedure.removeFromZKNamespaceManager(env, nsDescriptor.getName());
   } catch (Exception e) {
     // Ignore exception
     LOG.debug("Rollback of updateZKNamespaceManager throws exception: " + e);
   }
 }