Objects are not errors

You can't throw objects. You can only throw errors. 

Any parameter passed to the first argument of a `callback` must be an instanceof `Error`

```js
> throw { message: "str" }
[object Object]
> throw new Error("str")
Error: str
    at repl:1:7
    at REPLServer.self.eval (repl.js:110:21)
    at repl.js:249:20
    at REPLServer.self.eval (repl.js:122:7)
    at Interface.<anonymous> (repl.js:239:12)
    at Interface.EventEmitter.emit (events.js:95:17)
    at Interface._onLine (readline.js:202:10)
    at Interface._line (readline.js:531:8)
    at Interface._ttyWrite (readline.js:760:14)
    at ReadStream.onkeypress (readline.js:99:10)
```