better error checking on renew slice
better error checking on renew slice

GENI-NSF/gram,plantigrade/geni-tools,tcmitchell/geni-tools,plantigrade/geni-tools,GENI-NSF/gram,ahelsing/geni-tools,tcmitchell/geni-tools,ahelsing/geni-tools,GENI-NSF/gram