def get_s3_url(s3_client, bucket, key, expires_in=604800):
    """ Generate signed URL for specified object key in bucket
    """

    signed_url = s3_client.generate_presigned_url(
                    'get_object',
                    Params={
                        'Bucket': bucket,
                        'Key': key
                    },
                    ExpiresIn=expires_in
    )

    return signed_url