/*
 * call-seq:
 *    conn.error() -> String
 *
 * Returns the error message about connection.
 */
static VALUE
pgconn_error_message(VALUE self)
{
    char *error = PQerrorMessage(get_pgconn(self));
    if (!error) return Qnil;
    return rb_tainted_str_new2(error);
}