CDB-3695 better error reporting if missing download url
CDB-3695 better error reporting if missing download url

splashblot/dronedb,bloomberg/cartodb,dbirchak/cartodb,thorncp/cartodb,CartoDB/cartodb,thorncp/cartodb,codeandtheory/cartodb,UCL-ShippingGroup/cartodb-1,nuxcode/cartodb,codeandtheory/cartodb,dbirchak/cartodb,raquel-ucl/cartodb,splashblot/dronedb,future-analytics/cartodb,raquel-ucl/cartodb,DigitalCoder/cartodb,codeandtheory/cartodb,nuxcode/cartodb,nyimbi/cartodb,future-analytics/cartodb,UCL-ShippingGroup/cartodb-1,bloomberg/cartodb,DigitalCoder/cartodb,raquel-ucl/cartodb,bloomberg/cartodb,codeandtheory/cartodb,raquel-ucl/cartodb,CartoDB/cartodb,thorncp/cartodb,future-analytics/cartodb,bloomberg/cartodb,nuxcode/cartodb,DigitalCoder/cartodb,nuxcode/cartodb,CartoDB/cartodb,CartoDB/cartodb,nyimbi/cartodb,nyimbi/cartodb,nyimbi/cartodb,UCL-ShippingGroup/cartodb-1,DigitalCoder/cartodb,UCL-ShippingGroup/cartodb-1,codeandtheory/cartodb,thorncp/cartodb,UCL-ShippingGroup/cartodb-1,splashblot/dronedb,future-analytics/cartodb,DigitalCoder/cartodb,bloomberg/cartodb,dbirchak/cartodb,splashblot/dronedb,nyimbi/cartodb,CartoDB/cartodb,future-analytics/cartodb,thorncp/cartodb,dbirchak/cartodb,raquel-ucl/cartodb,splashblot/dronedb,nuxcode/cartodb,dbirchak/cartodb