Show nicer errors on some server failures.

utils/pub/pub.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.
 
 /**
  * The main entrypoint for the pub command line application.
  */
 #library('pub');
 
 #import('../../pkg/args/args.dart');
@@ skipping 159 matching lines @@
     try {
      commandOptions = commandParser.parse(commandArgs);
     } on FormatException catch (e) {
       this.printUsage(description: e.message);
       return;
     }
 
     handleError(error, trace) {
       // This is basically the top-level exception handler so that we don't
       // spew a stack trace on our users.
-      // TODO(rnystrom): Add --trace flag so stack traces can be enabled for
-      // debugging.
       var message = error.toString();
 
       // TODO(rnystrom): The default exception implementation class puts
       // "Exception:" in the output, so strip that off.
       if (message.startsWith("Exception: ")) {
         message = message.substring("Exception: ".length);
       }
 
       printError(message);
       if (globalOptions['trace'] && trace != null) {
@@ skipping 35 matching lines @@
     print('');
     print('Usage: $usage');
 
     var commandUsage = commandParser.getUsage();
     if (!commandUsage.isEmpty()) {
       print('');
       print(commandUsage);
     }
   }
 }