    # File lib/rubygems/spec_fetcher.rb, line 232
      def warn_legacy(exception)
        uri = exception.uri.to_s
        if uri =~ /specs\.#{Regexp.escape Gem.marshal_version}\.gz$/ then
          alert_warning "RubyGems 1.2+ index not found for:\n\\t\#{legacy_repos.join \"\\n\\t\"}\n\nRubyGems will revert to legacy indexes degrading performance.\n"

          yield

          return true
        end

        false
      end