    # File lib/chef/cookbook/synchronizer.rb, line 116
        def clear_obsoleted_cookbooks
          @events.cookbook_clean_start
          # Remove all cookbooks no longer relevant to this node
          cache.find(File.join(%w{cookbooks ** *})).each do |cache_file|
            cache_file =~ /^cookbooks\/([^\/]+)\//
            unless have_cookbook?($1)
              Chef::Log.info("Removing #{cache_file} from the cache; its cookbook is no longer needed on this client.")
              cache.delete(cache_file)
              @events.removed_cookbook_file(cache_file)
            end
          end
          @events.cookbook_clean_complete
        end