title: django model with two fields from another model
body: <p>I am creating model class Car and I want to have in it two references to one foreign key.</p>
  
  <pre><code>class Car(models.Model):
       owner = models.ForeignKey(User)
       #and here I want to have owner email (which is already set in class User)
       email = owner.email
  </code></pre>
  
  <p>But I don't know how to make reference to field of ForeignKey already used.
  I get this error:</p>
  
  <blockquote>
    <p>AttributeError: type object 'User' has no attribute 'email'</p>
  </blockquote>
  
  <p>Is there any way to do it?</p>