Two bits:

1. What is the expected type of the argument
2. Either reason or error would be better than exception

@jasnell I chose exception because that's what it is called in the code. If we want to change it, do we have to reach into the code to change it there too?

I don't like error for the document because then you have to explain that error will be passed as an argument to any listeners on the 'error' event, which can get confusing especially to new users. So I'd probably go with reason over error, but reason doesn't signal to the reader that it's an error the way exception does.

As for the type, it would seem to be expecting an Error object but it actually doesn't look like there's any enforcement in the code so you could probably send it anything at all. I mean, it's just an argument for a listener, so it's kinda sorta up to the end user, I suppose. Suggest that it should (rather than must) be an Error perhaps?