Return cURL errors on HTTP response codes >= 400.

By default the cURL extension does not trigger any error when fetching a
response with an HTTP code >= 400. Changing this behaviour is also useful to
intercept the 403 error generated when executing Redis commands disallowed
on Webdis by using ACLs.

lib/Predis/Network/WebdisConnection.php

@@ -61,6 +61,7 @@ class WebdisConnection implements IConnectionSingle {
 
     private function initializeCurl(IConnectionParameters $parameters) {
         $options = array(
+            CURLOPT_FAILONERROR => true,
             CURLOPT_CONNECTTIMEOUT_MS => $parameters->connection_timeout * 1000,
             CURLOPT_URL => "{$parameters->scheme}://{$parameters->host}:{$parameters->port}",
             CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,