    # File lib/chef/cookbook_version.rb, line 334
        def self.clear_obsoleted_cookbooks(cookbook_hash)
          # Remove all cookbooks no longer relevant to this node
          cache.find(File.join(%w{cookbooks ** *})).each do |cache_file|
            cache_file =~ /^cookbooks\/([^\/]+)\//
            unless cookbook_hash.has_key?($1)
              Chef::Log.info("Removing #{cache_file} from the cache; its cookbook is no longer needed on this client.")
              cache.delete(cache_file)
            end
          end
        end