SignedJwtAssertionCredentials返回＆＃34; AccessTokenRefreshError：unauthorized_client＆＃34;

Question

我正在为我的雇主开发一个使用Google API Python客户端的Python脚本。但是，我通过SignedJwtAssertionCredentials遇到OAuth身份验证问题。相关代码如下：

from apiclient.discovery import build
from oauth2client.client import SignedJwtAssertionCredentials

SERVICE_ACCOUNT_EMAIL = 'abunchofmumbojumbo@developer.gserviceaccount.com'
SERVICE_ACCOUNT_PKCS12_FILE_PATH = 'key.p12'
USER_EMAIL = 'emailaccountusedtoaccessdeveloperconsole@gmail.com'

f = file(SERVICE_ACCOUNT_PKCS12_FILE_PATH, 'rb')
key = f.read()
f.close()

credentials = SignedJwtAssertionCredentials(
  SERVICE_ACCOUNT_EMAIL,
  key,
  scope='https://www.googleapis.com/auth/youtube', 
  sub=USER_EMAIL)

http = httplib2.Http()
http = credentials.authorize(http)

service = build('youtube', 'v3', http=http)

这是Python执行代码时返回的内容：

oauth2client.client.AccessTokenRefreshError: unauthorized_client

我试图在线搜索我如何解决这个问题，但我找不到任何东西。我最好的猜测是我没有将正确的变量传递给SignedJwtAssertionCredentials，但我不完全确定是这种情况。任何帮助将不胜感激。