Print right message when OSDistroFieldNotFound exception raised
Print right message when OSDistroFieldNotFound exception raised

Change-Id: I082db208aa6ec91484aa416119b388fb165ff6dc
Closes-Bug: #1449821

sajuptpm/magnum,Tennyson53/magnum,paulczar/magnum,Tennyson53/SUR,mjbrewer/testindex,ArchiFleKs/magnum,Alzon/SUR,mjbrewer/testindex,Tennyson53/SUR,Tennyson53/magnum,openstack/magnum,annegentle/magnum,eshijia/magnum,dimtruck/magnum,eshijia/SUR,ffantast/magnum,ChengTiesheng/magnum,jay-lau/magnum,hongbin/magnum,openstack/magnum,ddepaoli3/magnum,Alzon/SUR,paulczar/magnum,dimtruck/magnum,ArchiFleKs/magnum,mjbrewer/testindex,sajuptpm/magnum,ffantast/magnum,annegentle/magnum,ramielrowe/magnum,eshijia/magnum,LaynePeng/magnum,eshijia/SUR,ChengTiesheng/magnum,hongbin/magnum,ddepaoli3/magnum,LaynePeng/magnum,ramielrowe/magnum