Python pickle.UnpicklingError:无效的加载键&x27；v'；Flask框架中的错误

我在Heroku部署了一个ML模型。但我正在申请

我从日志中得到以下错误

pickle.UnpicklingError:加载键“v”无效。“

（来自app.py）

2020-10-07T12:26:44.968109+00:00 app[web.1]: File "/app/app.py", line 6, in
2020-10-07T12:26:44.968110+00:00 app[web.1]: cv = pickle.load(open('cv-transform.pkl','rb'))
2020-10-07T12:26:44.968138+00:00 app[web.1]: _pickle.UnpicklingError: invalid load key, 'v'.

filename = 'model_moviewreview.pkl'
classifier = pickle.load(open(filename, 'rb'))
filename1 = 'cv-transform.pkl'
cv = pickle.load(open(filename1, 'rb'))