assert raw_exec: result.is_ok else print db.error
assert postgres_nfields: result.nfields == 4 else print_error db.error
assert postgres_fname: result.fname(0) == "uname" else print_error db.error
assert raw_exec: result.is_ok else print db.error
assert postgres_nfields: result.nfields == 4 else print_error db.error
assert postgres_fname: result.fname(0) == "uname" else print_error db.error