不久前，我开始使用yagmail通过GMail使用OAuth2发送邮件。
我使用的代码很简单：

def send_with_yagmail(self):
        yag = yagmail.SMTP(self.our_email, oauth2_file="/<path_to>/credentials.json")
        yag.send(self.to_email, self.message_subject, contents=self.message_body)

有几天一切都很好，但突然Gmail停止发送邮件，堆栈跟踪显示以下内容：

...
return get_oauth_string(user, oauth2_info)                            
File "/usr/local/lib/p│ython3.9/site-packages/yagmail/oauth2.py", line 96, in get_oauth_string
  access_token, expires_in = refresh_authorization(**oauth2_info)
File "/usr/local/lib/python3.9/site-packages/yagmail/oauth2.py", line 91, in refresh_authorization
  response = call_refresh_token(google_client_id, google_client_secret, google_refresh_token)
File "/usr/local/lib/python3.9/site-packages/yagmail/oauth2.py", line 71, in call_refresh_token
 response = urlopen(request_url, encoded_params).read().decode('UTF-8')
File "/usr/local/lib/python3.9/urllib/request.py", line 214, in urlopen 
  return opener.open(url, data, timeout)                                
File "/usr/local/lib/python3.9/urllib/request.py", line 523, in open    
  response = meth(req, response)                                        
File "/usr/local/lib/python3.9/urllib/request.py", line 632, in http_response
  response = self.parent.error(
File "/usr/local/lib/python3.9/urllib/request.py", line 561, in error   
  return self._call_chain(*args)
File "/usr/local/lib/python3.9/urllib/request.py", line 494, in _call_chain
  result = func(*args)│Ju
  File "/usr/local/lib/python3.9/urllib/request.py", line 641, in http_error_default
 raise HTTPError(req.full_url, code, msg, hdrs, fp)                    
urllib.error.HTTPError: HTTP Error 400: Bad Request

我已经解决了这个问题，在我的机器上重新生成了credentials.json，并上传到服务器，认为这是一个一次性的事件。它工作了几天，现在又停止工作了。所以我想知道：我应该怎么做才不用每隔几天就重新生成一次凭证？我的credentials.json看起来如下所示：

{
  "email_address": "my.team@gmail.com",
  "google_client_id": "74<blabla>0e1feov.apps.googleusercontent.com",
  "google_client_secret": "GOCSP<blabla<kOz",
  "google_refresh_token": "1//09<blabla>-2_dxZH8"
}

库使用刷新令牌的目的不是为了使我不必手动重新生成这个东西吗？
有谁能推荐一些可以做的事情吗？谢谢！