lib/errors/error.js
function RpcError(cause, msg) {
    var off = 0;
    if (cause instanceof Error)
        off = 1;

    var args = Array.prototype.slice.call(arguments, off);
    args.unshift({
        cause: off ? cause : undefined,
        ctor: RpcError
    });
    WError.apply(this, args);

    this.type = 1; // reply
}
function RpcError(cause, msg) {
    var off = 0;
    if (cause instanceof Error)
        off = 1;

    var args = Array.prototype.slice.call(arguments, off);
    args.unshift({
        cause: off ? cause : undefined,
        ctor: RpcError
    });
    WError.apply(this, args);

    this.type = 1; // reply
}
/--- API