I don't think that's a good solution, particularly since we (well, mostly @xaviershay) were involved in the Fivemat PR and signed off and it's been released.  Having to register a formatter like that twice is crappy.

I think there's an alternate way to implement this that avoids this problem:

``` ruby
def existing_formatter_implements?(notification)
  @reporter.registerd_listeners(notification).any?
end
```