title: Throwing exception on mongoose callback
body: <p>I'm developing a Node.js + Express. My database is Mongo, and I'm using Mongoose to connect to this database. </p>
  
  <p>I'm trying to throw an exception in a Mongoose query callback this way:</p>
  
  <pre><code>game.save(function (err) {
    if (err) {
      throw new app.exception.EntitySaveFailed();
    }          
  });
  </code></pre>
  
  <p>but when I do it, Node server crashes and shows this stacktrace:</p>
  
  <pre><code>[object Object]
      at Promise.&lt;anonymous&gt; (/home/server/routes/api/game.js:219:17)
      at Promise.&lt;anonymous&gt; (/home/server/node_modules/mongoose/node_modules/mpromise/lib/promise.js:162:8)
      at Promise.EventEmitter.emit (events.js:95:17)
      at Promise.emit (/home/server/node_modules/mongoose/node_modules/mpromise/lib/promise.js:79:38)
      at Promise.fulfill (/home/server/node_modules/mongoose/node_modules/mpromise/lib/promise.js:92:20)
      at Promise.resolve (/home/server/node_modules/mongoose/lib/promise.js:108:15)
      at Promise.&lt;anonymous&gt; (/home/server/node_modules/mongoose/node_modules/mpromise/lib/promise.js:162:8)
      at Promise.EventEmitter.emit (events.js:95:17)
      at Promise.emit (/home/server/node_modules/mongoose/node_modules/mpromise/lib/promise.js:79:38)
      at Promise.fulfill (/home/server/node_modules/mongoose/node_modules/mpromise/lib/promise.js:92:20)
  Forever detected script exited with code: 8
  Forever restarting script for 9389 time
  Listening on port 3000...
  </code></pre>
  
  <p>When I throw an exception outside a mongoose callback function, all works fine. </p>