Report Python errors from iterators with PLy_elog
Report Python errors from iterators with PLy_elog

This improves reporting, as the error string now includes the actual
Python exception. As a side effect, this no longer sets the errcode to
ERRCODE_DATA_EXCEPTION, which might be considered a feature, as it's
not documented and not clear why iterator errors should be treated
differently.

Jan Urbański

arcivanov/postgres-xl,tpostgres-projects/tPostgres,xinzweb/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,lisakowen/gpdb,zeroae/postgres-xl,arcivanov/postgres-xl,pavanvd/postgres-xl,jmcatamney/gpdb,jmcatamney/gpdb,zeroae/postgres-xl,kmjungersen/PostgresXL,adam8157/gpdb,techdragon/Postgres-XL,ovr/postgres-xl,postmind-net/postgres-xl,ashwinstar/gpdb,postmind-net/postgres-xl,tpostgres-projects/tPostgres,jmcatamney/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,snaga/postgres-xl,snaga/postgres-xl,xinzweb/gpdb,50wu/gpdb,50wu/gpdb,lisakowen/gpdb,jmcatamney/gpdb,50wu/gpdb,greenplum-db/gpdb,50wu/gpdb,adam8157/gpdb,greenplum-db/gpdb,50wu/gpdb,arcivanov/postgres-xl,arcivanov/postgres-xl,pavanvd/postgres-xl,ashwinstar/gpdb,Postgres-XL/Postgres-XL,zeroae/postgres-xl,lisakowen/gpdb,oberstet/postgres-xl,snaga/postgres-xl,adam8157/gpdb,adam8157/gpdb,pavanvd/postgres-xl,kmjungersen/PostgresXL,adam8157/gpdb,yazun/postgres-xl,arcivanov/postgres-xl,jmcatamney/gpdb,ashwinstar/gpdb,xinzweb/gpdb,xinzweb/gpdb,postmind-net/postgres-xl,pavanvd/postgres-xl,adam8157/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,arcivanov/postgres-xl,oberstet/postgres-xl,ovr/postgres-xl,tpostgres-projects/tPostgres,ovr/postgres-xl,snaga/postgres-xl,greenplum-db/gpdb,techdragon/Postgres-XL,adam8157/gpdb,jmcatamney/gpdb,kmjungersen/PostgresXL,lisakowen/gpdb,50wu/gpdb,yazun/postgres-xl,zeroae/postgres-xl,greenplum-db/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,ashwinstar/gpdb,oberstet/postgres-xl,ovr/postgres-xl,techdragon/Postgres-XL,ovr/postgres-xl,Postgres-XL/Postgres-XL,Postgres-XL/Postgres-XL,kmjungersen/PostgresXL,ashwinstar/gpdb,50wu/gpdb,jmcatamney/gpdb,postmind-net/postgres-xl,zeroae/postgres-xl,yazun/postgres-xl,Postgres-XL/Postgres-XL,lisakowen/gpdb,techdragon/Postgres-XL,tpostgres-projects/tPostgres,ashwinstar/gpdb,tpostgres-projects/tPostgres,greenplum-db/gpdb,postmind-net/postgres-xl,xinzweb/gpdb,jmcatamney/gpdb,techdragon/Postgres-XL,ashwinstar/gpdb,yazun/postgres-xl,yazun/postgres-xl,xinzweb/gpdb,xinzweb/gpdb,kmjungersen/PostgresXL,pavanvd/postgres-xl,snaga/postgres-xl