    # File lib/rubygems/spec_fetcher.rb, line 137
      def legacy_repos
        Gem.sources.reject do |source_uri|
          source_uri = URI.parse source_uri
          spec_path = source_uri + "specs.#{Gem.marshal_version}.gz"

          begin
            @fetcher.fetch_size spec_path
          rescue Gem::RemoteFetcher::FetchError
            begin
              @fetcher.fetch_size(source_uri + 'yaml') # re-raise if non-repo
            rescue Gem::RemoteFetcher::FetchError
              alert_error "#{source_uri} does not appear to be a repository"
              raise
            end
            false
          end
        end
      end