def disk_check_size(ctx, param, value):
    """ Validation callback for disk size parameter."""
    if value:
        # if we've got a prefix
        if isinstance(value, tuple):
            val = value[1]
        else:
            val = value
        if val % 1024:
            raise click.ClickException('Size must be a multiple of 1024.')
    return value
Validation callback for disk size parameter.