Get rid of all the library tags.

lib/src/barback/cycle_exception.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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.barback.cycle_exception;
-
 import '../exceptions.dart';
 
 /// An exception thrown when a transformer dependency cycle is detected.
 ///
 /// A cycle exception is usually produced within a deeply-nested series of
 /// calls. The API is designed to make it easy for each of these calls to add to
 /// the message so that the full reasoning for the cycle is made visible to the
 /// user.
 ///
 /// Each call's individual message is called a "step". A [CycleException] is
@@ skipping 34 matching lines @@
   CycleException._(this._step, this._next);
 
   /// Returns a copy of [this] with [step] added to the beginning of [steps].
   CycleException prependStep(String step) {
     if (_step == null) return new CycleException(step);
     return new CycleException._(step, this);
   }
 
   String toString() => message;
 }