Autotest has no output, unless a .rspec file exists

I can't remember exactly when this behavior changed, but it's easy to see with a modern RSpec:

1.  Create a `Gemfile` in an empty folder
2.  Add the gems `ZenTest` and `rspec`
3.  `bundle`
4.  `bundle exec autotest`

No output will be shown.  The workaround is to at least `touch .rspec`.

This is an annoying issue because no feedback is given about what the user needs to do.  At least one user has told me that RSpec doesn't work with `autotest` anymore after seeing this apparent "hang."