title: Prevent save button to submit form in Django admin
body: <p>I wrote a control over some input in my admin form, which is executed on save buttons' click (I control a repetition of some inputs, but that's not important). </p>
  
  <p>So, if this check fails, I alert a message, but I also need to avoid django admin to send this wrong request to the server. How can i do it in Javascript? (i'm using jQuery)</p>