title: Django pre_save signal - would an exception fail the transaction?
body: <p>I want to do some custom actions before a user is created. and I thought of using the <code>pre_save</code> signal for that. And in case one of those action would raise an exception stop the transaction, abort creating the user etc.</p>
  
  <ol>
  <li><p>Is this the way to go? would it abort the save if something fails in this step (this is the required behavior) I suspect so but couldn't find docs about it.</p></li>
  <li><p>What is the best practice for getting the future user.id. from my understanding it doesn't exists yet in pre-save but I need it as input for some of the extra custom actions.</p></li>
  </ol>
  
  <p>Thanks</p>