Clean up error handling.

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 'memory_source_file_helper.dart';
@@ skipping 19 matching lines @@
 };
 
 void runCompiler(Uri main) {
   Uri script = currentDirectory.resolve(nativeToUriPath(Platform.script));
   Uri libraryRoot = script.resolve('../../../sdk/');
 
   MemorySourceFileProvider.MEMORY_SOURCE_FILES = MEMORY_SOURCE_FILES;
   var provider = new MemorySourceFileProvider();
   var handler = new FormattingDiagnosticHandler(provider);
   var errors = [];
-  
+
   void diagnosticHandler(Uri uri, int begin, int end, String message,
                          Diagnostic kind) {
     if (kind == Diagnostic.ERROR) {
       errors.add(message);
     }
     handler(uri, begin, end, message, kind);
   }
-  
-  
+
+
   EventSink<String> outputProvider(String name, String extension) {
     if (name != '') throw 'Attempt to output file "$name.$extension"';
     return new NullSink('$name.$extension');
   }
 
   Compiler compiler = new Compiler(provider.readStringFromUri,
                                    outputProvider,
                                    diagnosticHandler,
                                    libraryRoot,
                                    null,
                                    []);
-  
+
   compiler.run(main);
   Expect.equals(1, errors.length);
-  Expect.equals("Error: Cannot resolve 'package:foo/foo.dart'. "
-                "Package root has not been set.", 
+  Expect.equals('Error: Cannot resolve "package:foo/foo.dart". '
+                'Package root has not been set.',
                 errors[0]);
 }
 
 void main() {
   runCompiler(Uri.parse('memory:main.dart'));
   runCompiler(Uri.parse('package:foo/foo.dart'));
 }