old_contents: from django.db.models.signals import post_save
  from devilry.devilry_account.models import User
  from django.conf import settings
  
  
  def set_email_by_username(sender, **kwargs):
      """
      Signal handler which is invoked when a User is saved.
      """
      user = kwargs['instance']
      if not user.email:
          user.email = '{0}@{1}'.format(user.username, settings.DEVILRY_DEFAULT_EMAIL_SUFFIX)
  
  post_save.connect(set_email_by_username,
                    sender=User)
  
new_contents: from django.conf import settings
  
  
  def set_email_by_username(sender, **kwargs):
      """
      Signal handler which is invoked when a User is saved.
      """
      user = kwargs['instance']
      if not user.email:
          user.email = '{0}@{1}'.format(user.username, settings.DEVILRY_DEFAULT_EMAIL_SUFFIX)
  
  # post_save.connect(set_email_by_username,
  #                   sender=User)
  
subject: Comment out the post_save connect line.