Not able to show errors with Ember 2

In an application built with Ember 2.1.0, I followed this guide to implement server side validation.

I have this route :

import Ember from 'ember';

export default Ember.Route.extend({
  model(params) {
    return this.store.findRecord('user', params.id);
  },
  actions: {
    submit: function() {
      this.controller.model.save().then(function() {
        this.transitionTo('admin.users');
      }, (data) => {
        console.log(data.errors);
        this.set('errors', data.errors);
      });
    },
    cancel: function() {
      this.controller.model.rollbackAttributes();
      this.transitionTo('admin.users');
    }
  }
});

And I have this code in the template :

  {{#if errors.length}}
    <div class='alert alert-danger'>
      <h4>There was a problem</h4>
      <p>The user could not be saved due to validation errors</p>
    </div>
  {{/if}}

The server returns {"errors":[{"email":["can't be blank"]}]} and errors are displayed in the console but nothing on the page.

According to the documentation, I tried to return {"errors":{"email":["can't be blank"]}} but I have "InvalidError expects json-api formatted errors array."

How can I show errors with Ember 2?