    # File lib/rubygems/doc_manager.rb, line 60
        def load_rdoc
          if File.exist?(@doc_dir) && !File.writable?(@doc_dir) then
            raise Gem::FilePermissionError.new(@doc_dir)
          end

          FileUtils.mkdir_p @doc_dir unless File.exist?(@doc_dir)

          begin
            gem 'rdoc'
          rescue Gem::LoadError
            # use built-in RDoc
          end

          begin
            require 'rdoc/rdoc'
          rescue LoadError => e
            raise Gem::DocumentError,
              "ERROR: RDoc documentation generator not installed!"
          end
        end