payload = json.loads(base64.b64decode(licBody.encode()).decode())
b64challenge = base64.b64encode(challenge).decode()
payload["getWidevineLicense"]["widevineChallenge"]=b64challenge
res = await (await pyfetch(licUrl,
    method="POST",
    headers=licHeaders,
    body=json.dumps(payload)
)).json()
licence = base64.b64decode(res["getWidevineLicenseResponse"]["license"].encode())