I blew away my bundle followed by a `rm -fr vendor/rspec-1` to test that `bundle exec rake` would properly exec `:submodules` before `:spec`.
The warning was a side-effect from the `rm`, which somebody would not normally do. 

I considered patching https://github.com/vcr/vcr/blob/master/vcr.gemspec#L13 with a ` - ['vendor/rspec-1']` since that file doesn't add anything to the gem.