Hmm…that’s not an error. If you mouse click the code editor, it will go away. 
Yes, the semicolon is my mistake. But it shouldn’t matter for testing because I am using the latest Chrome. It will handle ES6. ES6 ignores semicolons. But I don’t usually do that. Just this is in a hurry.
The way I test the hook is to use the Wix Database app and edit the collection directly. The console.log used to show on the Chrome Dev tool. As you can see, all the hooks in data.js is filled with console logs. I used to test all the previous hooks that way.
You may try to edit the ‘enrollment’ collection and change the ‘paidBy’ field. See if it shows in your Chrome Dev tool.
Thanks.