Add verbosity levels for warnings and errors.

lib/src/log.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.
 
 /// Message logging.
 library pub.log;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 93 matching lines @@
   /// Silence all logging.
   static const NONE = const Verbosity._("none", const {
     Level.ERROR:   null,
     Level.WARNING: null,
     Level.MESSAGE: null,
     Level.IO:      null,
     Level.SOLVER:  null,
     Level.FINE:    null
   });
 
+  /// Shows only errors.
+  static const ERROR = const Verbosity._("error", const {
+    Level.ERROR:   _logToStderr,
+    Level.WARNING: null,
+    Level.MESSAGE: null,
+    Level.IO:      null,
+    Level.SOLVER:  null,
+    Level.FINE:    null
+  });
+
   /// Shows only errors and warnings.
   static const WARNING = const Verbosity._("warning", const {
     Level.ERROR:   _logToStderr,
     Level.WARNING: _logToStderr,
     Level.MESSAGE: null,
     Level.IO:      null,
     Level.SOLVER:  null,
     Level.FINE:    null
   });
 
@@ skipping 414 matching lines @@
     this.message(errorJson);
   }
 
   /// Encodes [message] to JSON and prints it if JSON output is enabled.
   void message(message) {
     if (!enabled) return;
 
     print(JSON.encode(message));
   }
 }