Fix rake when cucumber gem is not present

Ensure `rake` works without the cucumber gem.

## Verification Steps

- [x] Run: `bundle install --without test`
- [x] VERIFY: `rake -T` lists tasks.  No stacktraces.
- [x] Run: `bundle config --delete without`
- [x] Run: `bundle install`
- [x] VERIFY: `rake -T` lists tasks.  No stacktraces.