erp5_notebook: Fail if we encounter non-py code blocks.

bt5/erp5_notebook/SkinTemplateItem/portal_skins/erp5_notebook/gadget_jsmd_eval.js.js

@@ -267,6 +267,8 @@
     if (language === 'py') {
       console.log(line_list);
       console.log("We are processing Python code!!!");
+    } else {
+      throw new Error('Unsupported code language: ' + language);
     }
   }