执行了以下代码

from flask import Flask, request, jsonify, make_response
from flask_restplus import Api, Resource, fields
from sklearn.externals import joblib
import numpy as np
import sys

flask_app = Flask(__name__)
app = Api(app = flask_app, 
          version = "1.0", 
          title = "ML React App", 
          description = "Predict results using a trained model")

name_space = app.namespace('prediction', description='Prediction APIs')

model = app.model('Prediction params', 
                  {'Recency': fields.Float(required = True, 
                                               description="Recency Value", 
                                               help="Recency Value cannot be blank"),
                  'Frequency': fields.Float(required = True, 
                                               description="Frequency Value", 
                                               help="Frequency Value cannot be blank"),
                  'Monetary': fields.Float(required = True, 
                                            description="Monetary Value", 
                                            help="Monetary Value cannot be blank"),
                  })

classifier = joblib.load('classifier.joblib')

@name_space.route("/")
class MainClass(Resource):

    def options(self):
        response = make_response()
        response.headers.add("Access-Control-Allow-Origin", "*")
        response.headers.add('Access-Control-Allow-Headers', "*")
        response.headers.add('Access-Control-Allow-Methods', "*")
        return response

    @app.expect(model)      
    def post(self):
        try: 
            formData = request.json
            data = [val for val in formData.values()]
            prediction = classifier.predict(np.array(data).reshape(1, -1))
            types = { 0: "Loyal", 1: "NotLoyal"}
            response = jsonify({
                "statusCode": 200,
                "status": "Prediction made",
                "result": "The type of Loyalty is: " + types[prediction[0]]
                })
            response.headers.add('Access-Control-Allow-Origin', '*')
            return response
        except Exception as error:
            return jsonify({
                "statusCode": 500,
                "status": "Could not make prediction",
                "error": str(error)
            })

收到以下错误。

错误:导入“app”时引发ImportError:

回溯（最近的最后一次调用）:
文件“d:\dilipan\clg\proj\ml-reacte-app-template-master\service\venv\lib\site-packages\flask\cli.py”，第240行，在locate_app
导入(module_name)
文件“d:\dilipan\clg\proj\ml-reacte-app-template-master\service\venv\lib\site-packages\sklearn.externals”，第3行，在从sklearn.externals导入作业库

两个月前，我在另一台pc上执行了同样的操作，运行良好。

无法从sklearn.externals导入joblib

任何一位都不胜感激。 提前谢谢你。