Switch pkg packages, pub, and dartdoc to use package: imports.

utils/pub/pub.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.
 
 /// The main entrypoint for the pub command line application.
 library pub;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:math';
 
-import '../../pkg/args/lib/args.dart';
-import '../../pkg/pathos/lib/path.dart' as path;
+import 'package:args/args.dart';
+import 'package:pathos/path.dart' as path;
 
 import 'command_help.dart';
 import 'command_install.dart';
 import 'command_lish.dart';
 import 'command_update.dart';
 import 'command_uploader.dart';
 import 'command_version.dart';
 import 'command_cache.dart';
 import 'entrypoint.dart';
 import 'exit_codes.dart' as exit_codes;
@@ skipping 298 matching lines @@
     if (exception is HttpException || exception is HttpParserException ||
         exception is SocketIOException || exception is PubHttpException) {
       return exit_codes.UNAVAILABLE;
     } else if (exception is FormatException) {
       return exit_codes.DATA;
     } else {
       return 1;
     }
   }
 }