Deploy a signature fole

def deploy_signature(source, dest, user=None, group=None):
    """Deploy a signature fole"""
    move(source, dest)
    os.chmod(dest, 0644)
    if user and group:
        try:
            uid = pwd.getpwnam(user).pw_uid
            gid = grp.getgrnam(group).gr_gid
            os.chown(dest, uid, gid)
        except (KeyError, OSError):
            pass