Use pub_server package

pkg/pub_server/lib/repository.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library pubserver.repository;
+library pub_server.repository;
 
 import 'dart:async';
 
 import 'package:pub_semver/pub_semver.dart';
 
 /// Represents information about a specific version of a pub package.
 class PackageVersion {
   /// The name of the package.
   final String packageName;
 
@@ skipping 94 matching lines @@
   /// Downloads a pub package.
   Future<Stream> download(String package, String version);
 
   /// Whether this package repository supports download URLs.
   bool get supportsDownloadUrl => false;
 
   /// A permanent download URL to a package (if supported).
   Future<Uri> downloadUrl(String package, String version)
       => new Future.error(new UnsupportedError('No download link support.'));
 }