Fixed new warning

        let priv_cert_bytes = include_bytes!("../test/cms.p12");

        let priv_cert = Pkcs12::from_der(priv_cert_bytes).expect("failed to load priv cert");

        let priv_cert = priv_cert

            .parse("mypass")

            .parse2("mypass")

            .expect("failed to parse priv cert");

        // sign cms message using public key cert

        let data = b"Hello world!";

        let mut cms = CmsContentInfo::sign(

            Some(&priv_cert.cert),

            Some(&priv_cert.pkey),

            Some(&priv_cert.cert.unwrap()),

            Some(&priv_cert.pkey.unwrap()),

            None,

            Some(data),

            CMSOptions::empty(),