Include command in ProcessException.

sdk/lib/io/process.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.
 
 // TODO(ager): The only reason for this class is that we
 // cannot patch a top-level at this point.
 class _ProcessUtils {
   external static _exit(int status);
 }
 
@@ skipping 196 matching lines @@
   static const ProcessSignal SIGPROF = const ProcessSignal._signal(27);
   static const ProcessSignal SIGPOLL = const ProcessSignal._signal(29);
   static const ProcessSignal SIGSYS = const ProcessSignal._signal(31);
 
   const ProcessSignal._signal(int this._signalNumber);
   final int _signalNumber;
 }
 
 
 class ProcessException implements Exception {
-  const ProcessException([String this.message = "", int this.errorCode = 0]);
-  String toString() => "ProcessException: $message ($errorCode)";
+  const ProcessException(String this.executable,
+                         List<String> this.arguments,
+                         [String this.message = "",
+                          int this.errorCode = 0]);
+  String toString() {
+    var msg = (message == null) ? 'OS error code: $errorCode' : message;
+    var args = Strings.join(arguments, ' ');
+    return "ProcessException: $msg\n  Command: $executable $args";
+  }
+
+  /**
+   * Contains the executable provided for the process.
+   */
+  final String executable;
+
+  /**
+   * Contains the arguments provided for the process.
+   */
+  final List<String> arguments;
 
   /**
    * Contains the system message for the process exception if any.
    */
   final String message;
 
   /**
    * Contains the OS error code for the process exception if any.
    */
   final int errorCode;
 }