Update unittest to new package layout.

utils/tests/pub/version_solver_test.dart

 // Copyright (c) 2012, 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('pub_update_test');
 
 #import('dart:io');
 #import('dart:isolate');
 
 #import('../../pub/lock_file.dart');
 #import('../../pub/package.dart');
 #import('../../pub/pubspec.dart');
 #import('../../pub/source.dart');
 #import('../../pub/source_registry.dart');
 #import('../../pub/utils.dart');
 #import('../../pub/version.dart');
 #import('../../pub/version_solver.dart');
-#import('../../../pkg/unittest/unittest.dart');
+#import('../../../pkg/unittest/lib/unittest.dart');
 
 final noVersion = 'no version';
 final disjointConstraint = 'disjoint';
 final sourceMismatch = 'source mismatch';
 final descriptionMismatch = 'description mismatch';
 final couldNotSolve = 'unsolved';
 
 Source source1;
 Source source2;
 Source versionlessSource;
@@ skipping 430 matching lines @@
 Pair<String, Source> parseSource(String name) {
   var match = new RegExp(@"(.*) from (.*)").firstMatch(name);
   if (match == null) return new Pair<String, Source>(name, source1);
   switch (match[2]) {
   case 'mock1': return new Pair<String, Source>(match[1], source1);
   case 'mock2': return new Pair<String, Source>(match[1], source2);
   case 'versionless':
     return new Pair<String, Source>(match[1], versionlessSource);
   }
 }