/// <summary>
 /// Called when a plugin source reports a lost plugin.
 /// </summary>
 /// <param name="sender">The sender.</param>
 /// <param name="e">The <see cref="PluginEventArgs"/> instance containing the event data.</param>
 private void OnPluginRemoved(object sender, PluginEventArgs e)
 {
     this.log.Info(Resources.RemovedPlugin, e.Plugin.QualifiedName.TypeFullName);
       this.plugins.Remove(e.Plugin);
 }