title: Equivalent of get_or_create for adding users
body: <p>Is there a simpler way to add a user than with the following pattern?</p>
  
  <pre><code>    try:
          new_user = User.objects.create_user(username, email, password)
      except IntegrityError:
          messages.info(request, "This user already exists.")
      else:
          new_user.first_name = first_name
          # continue with other things
  </code></pre>