def _get_version(ctx, _, value):
    """Click callback for option to show current ZSL version."""

    if not value or ctx.resilient_parsing:
        return
    message = 'Zsl %(version)s\nPython %(python_version)s'
    click.echo(message % {
        'version': version,
        'python_version': sys.version,
    }, color=ctx.color)
    ctx.exit()
Click callback for option to show current ZSL version.