Ruby 1.9 Pathname#cleanpath did not work correctly on windows. https://bugs.ruby-lang.org/issues/9618 This was fixed in ruby 2.0. Puppet 6.x requires ruby 2.3 or greater, so we should remove our workaround.
Merged to 6.x in https://github.com/puppetlabs/puppet/commit/fc1ece9b36205239a89f13c2c5f7feffc1cb3e6f