# File lib/chef/knife/cookbook_delete.rb, line 87
      def available_versions
        @available_versions ||= rest.get_rest("cookbooks/#{@cookbook_name}").map do |name, url_and_version|
          url_and_version["versions"].map {|url_by_version| url_by_version["version"]}
        end.flatten
      rescue Net::HTTPServerException => e
        if e.to_s =~ /^404/
          ui.error("Cannot find a cookbook named #{@cookbook_name} to delete")
          nil
        else
          raise
        end
      end