Doc about server exception option in ErrorPlugin

plugins/error.rst

@@ -36,3 +36,8 @@ writing a library around an API, the best practice is to have the client convert
 domain objects, and transform HTTP errors into meaningful domain exceptions. In that scenario,
 the ErrorPlugin is not needed. It is more efficient to check the HTTP status codes yourself than
 throwing and catching exceptions.
+
+If you need to handle 4XX responses, as having a 404 can have meaning in your http client, but sill want 
+exception for 5XX responses, you can set the ``only_server_exception`` option to ``true``::
+
+    $errorPlugin = new ErrorPlugin(['only_server_exception' => true]);