Use pub_semver package in pub.

sdk/lib/_internal/pub_generated/test/serve_packages.dart

 library serve_packages;
 import 'dart:async';
 import 'dart:convert';
 import 'package:path/path.dart' as p;
+import 'package:pub_semver/pub_semver.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:yaml/yaml.dart';
 import '../lib/src/io.dart';
 import '../lib/src/utils.dart';
-import '../lib/src/version.dart';
 import 'descriptor.dart' as d;
 import 'test_pub.dart';
 d.DirectoryDescriptor _servedApiPackageDir;
 d.DirectoryDescriptor _servedPackageDir;
 PackageServerBuilder _builder;
 void servePackages(void callback(PackageServerBuilder builder), {bool replace:
     false}) {
   if (_servedPackageDir == null) {
     _builder = new PackageServerBuilder();
     _servedApiPackageDir = d.dir('packages', []);
@@ skipping 84 matching lines @@
       _futures = new FutureGroup();
     });
   }
 }
 class _ServedPackage {
   final Map pubspec;
   final List<d.Descriptor> contents;
   Version get version => new Version.parse(pubspec['version']);
   _ServedPackage(this.pubspec, this.contents);
 }