try {
    /**
     * We use Guzzle to make an HTTP request somewhere in the
     * following theMethodMayThrowException().
     */
    $result = theMethodMayThrowException();
} catch (\GuzzleHttp\Exception\RequestException $e) {
    /**
     * Here we actually catch the instance of GuzzleHttp\Psr7\Response
     * (find it in ./vendor/guzzlehttp/psr7/src/Response.php) with all
     * its own and its 'Message' trait's methods. See more explanations below.
     *
     * So you can have: HTTP status code, message, headers and body.
     * Just check the exception object has the response before.
     */
    if ($e->hasResponse()) {
        $response = $e->getResponse();
        var_dump($response->getStatusCode()); // HTTP status code;
        var_dump($response->getReasonPhrase()); // Response message;
        var_dump((string) $response->getBody()); // Body, normally it is JSON;
        var_dump(json_decode((string) $response->getBody())); // Body as the decoded JSON;
        var_dump($response->getHeaders()); // Headers array;
        var_dump($response->hasHeader('Content-Type')); // Is the header presented?
        var_dump($response->getHeader('Content-Type')[0]); // Concrete header value;
    }
}
// process $result etc. ...