src/Client.php
protected function createErrorException( ResponseInterface $response ){

        $body = json_decode($response->getBody(), true);

        $message = "HTTP:{$response->getStatusCode()} - ";
        $message .= (is_array($body)) ? print_r($body, true) : 'Unexpected response from server';

        return new Exception\ApiException( $message, $response->getStatusCode(), $response );

    }
protected function createErrorException( ResponseInterface $response ){

        $body = json_decode($response->getBody(), true);

        $message = "HTTP:{$response->getStatusCode()} - ";
        $message .= (is_array($body)) ? print_r($body, true) : 'Unexpected response from server';

        return new Exception\ApiException( $message, $response->getStatusCode(), $response );

    }
Called with a response from the API when the response code was unsuccessful. i.e. not 20X.

@param ResponseInterface $response

@return Exception\ApiException