import time

import google.auth.crypt
import google.auth.jwt


def main(args):
    """Generates a signed JSON Web Token using a Google API Service Account."""
    signer = google.auth.crypt.RSASigner.from_service_account_file(
        args.service_account_file)
    now = int(time.time())
    payload = {
        # expire in one hour.
        "exp": now + 3600,
        "iat": now,
    }
    if args.iss: