title: Model Validation and catching the errors in form Django
body: <p>I want to write model validation in the model class not in the ModelForm in order to DRY.</p>
  
  <p>I managed to do this, but when I raise the <code>ValidationError</code> wether it's <code>django.forms.ValidationError</code> or <code>django.core.exception.ValidationError</code> it will break the page.</p>
  
  <p>How to show the error message without breaking the page. </p>