module.exports.handler = async function(event, context, callback) {
    try {
        const Bucket = event.Records[0].s3.bucket.name;
        const Key = event.Records[0].s3.object.key;
        console.log('Bucket', Bucket);
        console.log('Key', Key);

        const objectHead = await s3.headObject({ Bucket, Key }).promise();
        console.log('Alas! I will never discover that the objectHead is:', objectHead);

        callback();
    } catch(err) {
        console.error('Error', err);
        callback(err);
    }
}

{
    NotFound: null
    message: null,
    code: 'NotFound',
    region: null,
    time: 2018-02-19T11:06:35.894Z,
    requestId: 'XXXXXXXXXXX',
    extendedRequestId: 'XXX.....XXX',
    cfId: undefined,
    statusCode: 404,
    retryable: false,
    retryDelay: 77.24564264820208
}

const s3 = new AWS.S3({
    region: 'us-east-1'
});