Comment 8 for bug 1670549

hello Sai, would you please add more debug code in plugins/standard.py:_validate_interfaces()

         if not result:
+ LOG.error("pxe_mac %s" % pxe_mac)
             raise utils.Error(_('No suitable interfaces found in %s') %
                               interfaces, data=data)

If some nodes fails, we can get pxe_mac and interfaces values, these two variables are very important for debugging.