Run "pub run" against the .packages file.

lib/src/entrypoint.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.entrypoint;
 
 import 'dart:async';
 
 import 'package:path/path.dart' as path;
 import 'package:barback/barback.dart';
@@ skipping 58 matching lines @@
         cache = cache,
         _packageSymlinks = packageSymlinks;
 
   /// Creates an entrypoint given package and lockfile objects.
   Entrypoint.inMemory(this.root, this._lockFile, this.cache)
       : _packageSymlinks = false;
 
   /// The path to the entrypoint's "packages" directory.
   String get packagesDir => root.path('packages');
 
+  /// The path to the entrypoint's ".packages" file.
+  String get packagesFile => root.path('.packages');
+
   /// `true` if the entrypoint package currently has a lock file.
   bool get lockFileExists => _lockFile != null || entryExists(lockFilePath);
 
   LockFile get lockFile {
     if (_lockFile != null) return _lockFile;
 
     if (!lockFileExists) {
       _lockFile = new LockFile.empty();
     } else {
       _lockFile = new LockFile.load(lockFilePath, cache.sources);
@@ skipping 460 matching lines @@
   /// If [packageSymlinks] is true, creates a symlink to the "packages"
   /// directory in [dir].
   ///
   /// Otherwise, deletes a "packages" directories in [dir] if one exists.
   void _linkOrDeleteSecondaryPackageDir(String dir) {
     var symlink = path.join(dir, 'packages');
     if (entryExists(symlink)) deleteEntry(symlink);
     if (_packageSymlinks) createSymlink(packagesDir, symlink, relative: true);
   }
 }