'Creates a new ``activation_key`` resetting activation timeframe when
users let the previous key expire.
:param activation_key:
String containing the secret SHA1 activation key.'

def reissue_activation(self, activation_key):

    try:
        userena = self.get(activation_key=activation_key)
    except self.model.DoesNotExist:
        return False
    try:
        (salt, new_activation_key) = generate_sha1(userena.user.username)
        userena.activation_key = new_activation_key
        userena.save(using=self._db)
        userena.user.date_joined = get_datetime_now()
        userena.user.save(using=self._db)
        userena.send_activation_email()
        return True
    except Exception:
        return False
