code: func (c *TokenCommand) Del(client auth.ClientI) error {
  	if c.value == "" {
  		return trace.Errorf("Need an argument: token")
  	}
  	if err := client.DeleteToken(c.value); err != nil {
  		return trace.Wrap(err)
  	}
  	fmt.Printf("Token %s has been deleted\n", c.value)
  	return nil
  }
docs: // Del is called to execute "tokens del ..." command.