public function assertResponseBodyIsNot(PyStringNode $content) {
        $this->requireResponse();
        $content = (string) $content;

        try {
            Assertion::notSame((string) $this->response->getBody(), $content, sprintf(
                'Did not expect response body to be "%s".',
                $content
            ));
        } catch (AssertionFailure $e) {
            throw new AssertionFailedException($e->getMessage());
        }
    }