Clarify some error messages
Clarify some error messages

kaknikhil/gpdb,edespino/gpdb,janebeckman/gpdb,zeroae/postgres-xl,tangp3/gpdb,zaksoup/gpdb,lisakowen/gpdb,ahachete/gpdb,cjcjameson/gpdb,tangp3/gpdb,arcivanov/postgres-xl,zeroae/postgres-xl,xinzweb/gpdb,50wu/gpdb,royc1/gpdb,zaksoup/gpdb,yuanzhao/gpdb,techdragon/Postgres-XL,tangp3/gpdb,50wu/gpdb,cjcjameson/gpdb,0x0FFF/gpdb,Quikling/gpdb,Postgres-XL/Postgres-XL,lintzc/gpdb,randomtask1155/gpdb,lisakowen/gpdb,rubikloud/gpdb,arcivanov/postgres-xl,ahachete/gpdb,yuanzhao/gpdb,snaga/postgres-xl,janebeckman/gpdb,atris/gpdb,techdragon/Postgres-XL,arcivanov/postgres-xl,janebeckman/gpdb,foyzur/gpdb,ahachete/gpdb,Chibin/gpdb,chrishajas/gpdb,snaga/postgres-xl,adam8157/gpdb,Chibin/gpdb,janebeckman/gpdb,randomtask1155/gpdb,lpetrov-pivotal/gpdb,kaknikhil/gpdb,CraigHarris/gpdb,chrishajas/gpdb,lintzc/gpdb,chrishajas/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,tangp3/gpdb,chrishajas/gpdb,tangp3/gpdb,ashwinstar/gpdb,pavanvd/postgres-xl,zaksoup/gpdb,yazun/postgres-xl,rvs/gpdb,xuegang/gpdb,arcivanov/postgres-xl,lpetrov-pivotal/gpdb,rvs/gpdb,lpetrov-pivotal/gpdb,rvs/gpdb,kaknikhil/gpdb,lintzc/gpdb,royc1/gpdb,CraigHarris/gpdb,atris/gpdb,kaknikhil/gpdb,edespino/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,yuanzhao/gpdb,ahachete/gpdb,adam8157/gpdb,randomtask1155/gpdb,xuegang/gpdb,0x0FFF/gpdb,rubikloud/gpdb,jmcatamney/gpdb,techdragon/Postgres-XL,lpetrov-pivotal/gpdb,foyzur/gpdb,kaknikhil/gpdb,xuegang/gpdb,tangp3/gpdb,janebeckman/gpdb,snaga/postgres-xl,0x0FFF/gpdb,ahachete/gpdb,rvs/gpdb,edespino/gpdb,ahachete/gpdb,foyzur/gpdb,yuanzhao/gpdb,lisakowen/gpdb,royc1/gpdb,chrishajas/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,lisakowen/gpdb,CraigHarris/gpdb,oberstet/postgres-xl,snaga/postgres-xl,50wu/gpdb,edespino/gpdb,chrishajas/gpdb,atris/gpdb,0x0FFF/gpdb,Chibin/gpdb,zeroae/postgres-xl,yuanzhao/gpdb,yuanzhao/gpdb,rubikloud/gpdb,ashwinstar/gpdb,CraigHarris/gpdb,ovr/postgres-xl,kaknikhil/gpdb,ahachete/gpdb,lintzc/gpdb,rubikloud/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,50wu/gpdb,rvs/gpdb,yazun/postgres-xl,postmind-net/postgres-xl,oberstet/postgres-xl,techdragon/Postgres-XL,yuanzhao/gpdb,xuegang/gpdb,foyzur/gpdb,Chibin/gpdb,foyzur/gpdb,xinzweb/gpdb,kaknikhil/gpdb,arcivanov/postgres-xl,xinzweb/gpdb,cjcjameson/gpdb,edespino/gpdb,Quikling/gpdb,rvs/gpdb,lisakowen/gpdb,Chibin/gpdb,Chibin/gpdb,kaknikhil/gpdb,adam8157/gpdb,xuegang/gpdb,kmjungersen/PostgresXL,CraigHarris/gpdb,janebeckman/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,Postgres-XL/Postgres-XL,xinzweb/gpdb,lpetrov-pivotal/gpdb,postmind-net/postgres-xl,yazun/postgres-xl,arcivanov/postgres-xl,zaksoup/gpdb,greenplum-db/gpdb,xuegang/gpdb,zaksoup/gpdb,jmcatamney/gpdb,pavanvd/postgres-xl,zaksoup/gpdb,tpostgres-projects/tPostgres,Chibin/gpdb,Chibin/gpdb,CraigHarris/gpdb,ashwinstar/gpdb,tangp3/gpdb,royc1/gpdb,jmcatamney/gpdb,yazun/postgres-xl,adam8157/gpdb,foyzur/gpdb,atris/gpdb,Quikling/gpdb,Postgres-XL/Postgres-XL,rubikloud/gpdb,atris/gpdb,tpostgres-projects/tPostgres,ashwinstar/gpdb,jmcatamney/gpdb,lisakowen/gpdb,cjcjameson/gpdb,kmjungersen/PostgresXL,edespino/gpdb,greenplum-db/gpdb,50wu/gpdb,CraigHarris/gpdb,xuegang/gpdb,tangp3/gpdb,postmind-net/postgres-xl,kmjungersen/PostgresXL,kaknikhil/gpdb,janebeckman/gpdb,randomtask1155/gpdb,oberstet/postgres-xl,royc1/gpdb,adam8157/gpdb,Quikling/gpdb,ovr/postgres-xl,Quikling/gpdb,kmjungersen/PostgresXL,zaksoup/gpdb,50wu/gpdb,50wu/gpdb,royc1/gpdb,edespino/gpdb,ovr/postgres-xl,lintzc/gpdb,Quikling/gpdb,foyzur/gpdb,Postgres-XL/Postgres-XL,pavanvd/postgres-xl,lintzc/gpdb,50wu/gpdb,yuanzhao/gpdb,postmind-net/postgres-xl,0x0FFF/gpdb,oberstet/postgres-xl,xinzweb/gpdb,lintzc/gpdb,zaksoup/gpdb,foyzur/gpdb,0x0FFF/gpdb,Chibin/gpdb,randomtask1155/gpdb,pavanvd/postgres-xl,zeroae/postgres-xl,kaknikhil/gpdb,0x0FFF/gpdb,postmind-net/postgres-xl,ovr/postgres-xl,yazun/postgres-xl,atris/gpdb,adam8157/gpdb,janebeckman/gpdb,lisakowen/gpdb,rvs/gpdb,tpostgres-projects/tPostgres,edespino/gpdb,ahachete/gpdb,rvs/gpdb,xuegang/gpdb,techdragon/Postgres-XL,cjcjameson/gpdb,xinzweb/gpdb,0x0FFF/gpdb,royc1/gpdb,adam8157/gpdb,atris/gpdb,randomtask1155/gpdb,Chibin/gpdb,ashwinstar/gpdb,Quikling/gpdb,royc1/gpdb,Quikling/gpdb,xuegang/gpdb,atris/gpdb,Quikling/gpdb,chrishajas/gpdb,adam8157/gpdb,pavanvd/postgres-xl,snaga/postgres-xl,rvs/gpdb,zeroae/postgres-xl,Postgres-XL/Postgres-XL,ovr/postgres-xl,kmjungersen/PostgresXL,edespino/gpdb,rubikloud/gpdb,rubikloud/gpdb,tpostgres-projects/tPostgres,jmcatamney/gpdb,janebeckman/gpdb,greenplum-db/gpdb,randomtask1155/gpdb,lpetrov-pivotal/gpdb,cjcjameson/gpdb,lpetrov-pivotal/gpdb,randomtask1155/gpdb,chrishajas/gpdb,rubikloud/gpdb,ashwinstar/gpdb,edespino/gpdb,jmcatamney/gpdb,janebeckman/gpdb,lisakowen/gpdb,cjcjameson/gpdb,tpostgres-projects/tPostgres,lintzc/gpdb,Quikling/gpdb,lpetrov-pivotal/gpdb,ashwinstar/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,CraigHarris/gpdb,CraigHarris/gpdb,rvs/gpdb,lintzc/gpdb