Guzzle 6.x

Per the docs, the exception types you may need to catch are:

• GuzzleHttp\Exception\ClientException for 400-level errors
• GuzzleHttp\Exception\ServerException for 500-level errors
• GuzzleHttp\Exception\BadResponseException for both (it’s their superclass)

Code to handle such errors thus now looks something like this:

$client = new GuzzleHttp\Client;
try {
    $client->get('http://google.com/nosuchpage');    
}
catch (GuzzleHttp\Exception\ClientException $e) {
    $response = $e->getResponse();
    $responseBodyAsString = $response->getBody()->getContents();
}