Change the default shell of the user

    CLI Example:

    .. code-block:: bash

        salt '*' user.chshell foo /bin/zsh

def chshell(name, shell):
    '''
    Change the default shell of the user

    CLI Example:

    .. code-block:: bash

        salt '*' user.chshell foo /bin/zsh
    '''
    pre_info = info(name)
    if not pre_info:
        raise CommandExecutionError(
            'User \'{0}\' does not exist'.format(name)
        )
    if shell == pre_info['shell']:
        return True
    cmd = ['usermod', '-s', shell, name]
    __salt__['cmd.run'](cmd, python_shell=False)
    return info(name).get('shell') == shell