def login_user(sender, user, request, **kwargs):
    """ Automatically authenticate the user when activated  """
    backend = get_backends()[0]  # Hack to bypass `authenticate()`.
    user.backend = (backend.__module__, backend.__class__.__name__) % "%s.%s"
    login(request, user)
    request.session['REGISTRATION_AUTO_LOGIN'] = True
    request.session.modified = True
dataset/ETHPy150Open macropin/django-registration/registration/signals.py/login_user/swapped operands of `%`