Change the username for a named user

    name
        User to modify

    new_name
        New value of the login name

    root
        Directory to chroot into

    CLI Example:

    .. code-block:: bash

        salt '*' user.rename name new_name

def rename(name, new_name, root=None):
    '''
    Change the username for a named user

    name
        User to modify

    new_name
        New value of the login name

    root
        Directory to chroot into

    CLI Example:

    .. code-block:: bash

        salt '*' user.rename name new_name
    '''
    if info(new_name, root=root):
        raise CommandExecutionError('User \'{0}\' already exists'.format(new_name))

    return _chattrib(name, 'name', new_name, '-l', root=root)