Recover from read errors.

dart/tests/compiler/dart2js/package_root_test.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.
 
 // Test that the compiler can handle imports when package root has not been set.
 
 library dart2js.test.package_root;
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
@@ skipping 42 matching lines @@
   Compiler compiler = new Compiler(provider,
                                    outputProvider,
                                    diagnosticHandler,
                                    libraryRoot,
                                    packageRoot,
                                    [],
                                    {});
 
   asyncTest(() => compiler.run(main).then((_) {
     Expect.equals(1, errors.length);
-    Expect.isTrue(
-        errors[0].startsWith(
-            "Can't read 'package:foo/foo.dart' (Error reading "));
+    Expect.isTrue(errors[0].contains("Error reading "));
   }));
 }
 
 void main() {
   runCompiler(Uri.parse('memory:main.dart'));
   runCompiler(Uri.parse('package:foo/foo.dart'));
 }