Get rid of all the library tags.

lib/src/source/path.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.
 
-library pub.source.path;
-
 import 'dart:async';
 
 import 'package:path/path.dart' as p;
 import 'package:pub_semver/pub_semver.dart';
 
 import '../exceptions.dart';
 import '../io.dart';
 import '../package.dart';
 import '../pubspec.dart';
 import '../source.dart';
@@ skipping 148 matching lines @@
 
     if (fileExists(dir)) {
       fail('Path dependency for package $name must refer to a directory, '
            'not a file. Was "$dir".');
     }
 
     throw new PackageNotFoundException(
         'Could not find package $name at "$dir".');
   }
 }