Added missing HTTP status code 418

src/Symfony/Component/HttpFoundation/Response.php

@@ -64,6 +64,7 @@ class Response
         415 => 'Unsupported Media Type',
         416 => 'Requested Range Not Satisfiable',
         417 => 'Expectation Failed',
+        418 => 'I\'m a teapot',
         500 => 'Internal Server Error',
         501 => 'Not Implemented',
         502 => 'Bad Gateway',