title: Error handler not called for promise
body: <p>I have a service, which fails when I enter bad login credentials. However, my Promise error handler does not get called.</p>
  
  <p>I don't seem to grasp what's wrong with my code so that the <code>error</code> callback is never reached.</p>
  
  <h3>Service</h3>
  
  <pre><code>func loadRepositories() -&gt; Promise&lt;[Repository]&gt;{
      return Promise { fullfill, reject in
          manager.request(Method.GET, baseURL + "/api/1.0/user/repositories")
              .authenticate(user: username, password: password)
              .responseArray { (response: Response&lt;[Repository], NSError&gt;) in
                  switch response.result{
                  case .Success(let value):
                      fullfill(value)
                  case .Failure(let e):
                      // The breakpoint here is reached.
                      reject(e)
                  }
          }
      }
  }
  </code></pre>
  
  <h3>Handling</h3>
  
  <pre><code>firstly{
      service!.loadRepositories()
  }.then { repositories -&gt; Void in
      loginVC.dismissViewControllerAnimated(true, completion: nil)
      self.onLoginSuccessful()
  }.always{
      // Always gets called 
      loginVC.isSigningIn = false
  }.error { error in
      // I never get here even though `reject(e)` is called from the service.
      loginVC.errorString = "Login went wrong"
  }
  </code></pre>