src/Client/CurlHttpClient.php
private function checkServerError(ResponseInterface $response, RequestInterface $request)
    {
        if ($response->getStatusCode() >= 500) {
            throw new ServerErrorException($request, $response);
        }
    }
private function checkServerError(ResponseInterface $response, RequestInterface $request)
    {
        if ($response->getStatusCode() >= 500) {
            throw new ServerErrorException($request, $response);
        }
    }
Checks provided response is an HTTP server error (5xx)

@param ResponseInterface $response
@param RequestInterface $request

@throws ServerErrorException for responses with status codes grater or equal to 500