/*
 * call-seq:
 *    res.error_message() -> String
 *
 * Returns the error message of the command as a string. 
 */
static VALUE
pgresult_error_message(VALUE self)
{
        VALUE ret = rb_tainted_str_new2(PQresultErrorMessage(get_pgresult(self)));
        ASSOCIATE_INDEX(ret, self);
        return ret;
}