Per the docs, the exception types you may need to catch are:
GuzzleHttp\Exception\ClientException
for 400-level errorsGuzzleHttp\Exception\ServerException
for 500-level errorsGuzzleHttp\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();
}