Workaround #6986.

utils/pub/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 entrypoint;
 
 import 'io.dart';
 import 'lock_file.dart';
 import 'log.dart' as log;
 import 'package.dart';
@@ skipping 149 matching lines @@
   }
 
   /**
    * Loads the list of concrete package versions from the `pubspec.lock`, if it
    * exists. If it doesn't, this completes to an empty [LockFile].
    *
    * If there's an error reading the `pubspec.lock` file, this will print a
    * warning message and act as though the file doesn't exist.
    */
   Future<LockFile> _loadLockFile() {
-    var completer = new Completer<LockFile>();
     var lockFilePath = join(root.dir, 'pubspec.lock');
 
     log.fine("Loading lockfile.");
-    var future = readTextFile(lockFilePath);
+    return fileExists(lockFilePath).chain((exists) {
+      if (!exists) {
+        log.fine("No lock file at $lockFilePath, creating empty one.");
+        return new Future<LockFile>.immediate(new LockFile.empty());
+      }
 
-    future.handleException((_) {
-      // If we failed to load the lockfile but it does exist, something's
-      // probably wrong and we should notify the user.
-      fileExists(lockFilePath).transform((exists) {
-        if (!exists) return;
-        log.error("Error reading pubspec.lock: ${future.exception}");
-      }).then((_) {
-        log.fine("No lock file at $lockFilePath, creating empty one.");
-        completer.complete(new LockFile.empty());
-      });
-
-      return true;
+      return readTextFile(lockFilePath).transform((text) =>
+          new LockFile.parse(text, cache.sources));
     });
-
-    future.then((text) =>
-        completer.complete(new LockFile.parse(text, cache.sources)));
-    return completer.future;
   }
 
   /**
    * Saves a list of concrete package versions to the `pubspec.lock` file.
    */
   Future _saveLockFile(List<PackageId> packageIds) {
     var lockFile = new LockFile.empty();
     for (var id in packageIds) {
       if (id.source is! RootSource) lockFile.packages[id.name] = id;
     }
@@ skipping 83 matching lines @@
    * Creates a symlink to the `packages` directory in [dir] if none exists.
    */
   Future _linkSecondaryPackageDir(String dir) {
     var to = join(dir, 'packages');
     return exists(to).chain((exists) {
       if (exists) return new Future.immediate(null);
       return createSymlink(path, to);
     });
   }
 }