def METHOD_NAME(self, mock_mailchimp_client):
    del settings.MAILCHIMP_API_KEY
    subscriber_email = 'test@example.com'
    instance = mock_mailchimp_client.return_value
    instance.lists = mock.PropertyMock()
    with self.assertRaises(ApiKeyMissingError):
        subscribe_for_site(self.site, subscriber_email)
    instance.set_config.assert_not_called()
    instance.lists.set_list_member.assert_not_called()