Use pub_semver package in pub.

sdk/lib/_internal/pub/test/test_pub.dart

 // Copyright (c) 2013, 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.
 
 /// Test infrastructure for testing pub.
 ///
 /// Unlike typical unit tests, most pub tests are integration tests that stage
 /// some stuff on the file system, run pub, and then validate the results. This
 /// library provides an API to build tests like that.
 library test_pub;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'dart:math';
 
 import 'package:http/testing.dart';
 import 'package:path/path.dart' as p;
+import 'package:pub_semver/pub_semver.dart';
 import 'package:scheduled_test/scheduled_process.dart';
 import 'package:scheduled_test/scheduled_server.dart';
 import 'package:scheduled_test/scheduled_stream.dart';
 import 'package:scheduled_test/scheduled_test.dart' hide fail;
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf/shelf_io.dart' as shelf_io;
 import 'package:unittest/compact_vm_config.dart';
 import 'package:yaml/yaml.dart';
 
 import '../lib/src/entrypoint.dart';
 import '../lib/src/exit_codes.dart' as exit_codes;
 // TODO(rnystrom): Using "gitlib" as the prefix here is ugly, but "git" collides
 // with the git descriptor method. Maybe we should try to clean up the top level
 // scope a bit?
 import '../lib/src/git.dart' as gitlib;
 import '../lib/src/http.dart';
 import '../lib/src/io.dart';
 import '../lib/src/lock_file.dart';
 import '../lib/src/log.dart' as log;
 import '../lib/src/package.dart';
 import '../lib/src/pubspec.dart';
 import '../lib/src/source/hosted.dart';
 import '../lib/src/source/path.dart';
 import '../lib/src/source_registry.dart';
 import '../lib/src/system_cache.dart';
 import '../lib/src/utils.dart';
 import '../lib/src/validator.dart';
-import '../lib/src/version.dart';
 import 'descriptor.dart' as d;
 import 'serve_packages.dart';
 
 export 'serve_packages.dart';
 
 /// This should be called at the top of a test file to set up an appropriate
 /// test configuration for the machine running the tests.
 initConfig() {
   useCompactVMConfiguration();
   filterStacks = true;
@@ skipping 920 matching lines @@
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     return description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }
 
 /// A [StreamMatcher] that matches multiple lines of output.
 StreamMatcher emitsLines(String output) => inOrder(output.split("\n"));