title: Change ChoiceField option after clean method in Django form
body: <p>Is there any way to change a form element after the form is cleaned?</p>
  
  <p>There's some form logic that is affected by other fields. In certain cases I want to add an additional choice to a <code>ChoiceField</code> after the clean function runs if the form is invalid. Is there a way to do this?</p>