title: Rosbridge and roslibjs: Unable to load the manifest for package
body: <p>I'm trying the communication between javascript and Ros.</p>
  
  <p>I use the example code of 
  "github.com/RobotWebTools/roslibjs/blob/develop/examples/simple.html "
  with these changes:</p>
  
  <pre><code>var cmdVel = new ROSLIB.Topic({
      ros : ros,
      name : '/fromRos2Can',
      messageType : 'ackermann_msgs/AckermannDrive'    
    });
  </code></pre>
  
  <p>and</p>
  
  <pre><code> var twist = new ROSLIB.Message({
      speed:1.0,
      acceleration:2.0,
      jerk:3.0,
      steering_angle:4.0,
      steering_angle_velocity:5.2
    });
  </code></pre>
  
  <p>and I receive these two error message:    </p>
  
  <pre><code>[ERROR] [WallTime: 1404116229.210210] [Client 2] [id: advertise:/fromRos2Can:1] advertise: Unable to load the manifest for package ackermann_msgs. Caused by: ackermann_msgs
  
  [ERROR] [WallTime: 1404116229.213060] [Client 2] [id: publish:/fromRos2Can:2] publish: Cannot infer topic type for topic /fromRos2Can as it is not yet advertised
  </code></pre>
  
  <p><strong>My c++ program works with AckermannDrive.msg</strong> and a <strong>test with a std_msg/String works too</strong>.</p>
  
  <p>Where is my mistake?
  Thanks</p>