On my RHEL machine I have puppet and facter installed via RPMS. When I installed rspec-hiera-puppet (via gem) it forcibly installed both gems slapping itself on top of the rpm copies. Is there any chance you could remove this (or detect puppet differently) for people with packaged versions?
gem install rspec-hiera-puppet --ignore-dependencies
And you can find its deps through
gem dependency rspec-hiera-puppet