这个问题在这里已经有答案了：

flask view return error“查看函数未返回响应”（2个答案）
4个月前关门了。
我有一个flask应用程序，可以将用户数据添加到mysql数据库。我剧本里的每件事似乎都很好。我想要的数据被添加到mysql数据库中。但是，我得到以下错误：

127.0.0.1 - - [28/Jun/2018 12:19:44] "GET /protected HTTP/1.1" 500 -
Traceback (most recent call last):
  File "/Users/open/venv/FlaskMiddleware/lib/python2.7/site-packages/flask/app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Users/open/venv/FlaskMiddleware/lib/python2.7/site-packages/flask/app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "/Users/open/venv/FlaskMiddleware/lib/python2.7/site-packages/flask_restful/__init__.py", line 273, in error_router
    return original_handler(e)
  File "/Users/open/venv/FlaskMiddleware/lib/python2.7/site-packages/flask/app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/open/venv/FlaskMiddleware/lib/python2.7/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/open/venv/FlaskMiddleware/lib/python2.7/site-packages/flask/app.py", line 1816, in full_dispatch_request
    return self.finalize_request(rv)
  File "/Users/open/venv/FlaskMiddleware/lib/python2.7/site-packages/flask/app.py", line 1831, in finalize_request
    response = self.make_response(rv)
  File "/Users/open/venv/FlaskMiddleware/lib/python2.7/site-packages/flask/app.py", line 1957, in make_response
    'The view function did not return a valid response. The'
TypeError: The view function did not return a valid response. The function either returned None or ended without a return statement.

我真的不明白为什么我会犯这个错误。
这是我的密码：

from flask import Flask, request, jsonify, session
from flask_restful import Resource, Api
from werkzeug.security import generate_password_hash, check_password_hash
import mysqldb
from flask_jwt_extended import (
    JWTManager, jwt_required, create_access_token,
    get_jwt_identity
)

app = Flask(__name__)
app.config['SECRET_KEY'] = 'super-secret'
jwt = JWTManager(app)

api = Api(app, prefix="/api/v1")

USER_DATA = {
    "user1": "abc123",
    "user2":"userpass"
}

@app.route('/login', methods=['POST'])
def login():
    if not request.is_json:
        return jsonify({"msg": "Missing JSON in request"}), 400

    username = request.json.get('username', None)
    password = request.json.get('password', None)
    if not username:
        return jsonify({"msg": "Missing username parameter"}), 400
    if not password:
        return jsonify({"msg": "Missing password parameter"}), 400

    if username != USER_DATA.get(username) and password not in USER_DATA[username]:
        return jsonify({"msg": "Bad username or password"}), 401

    access_token = create_access_token({'first_name': request.json.get('Client First Name', None), 'last_name': request.json.get('Client Last Name', None)})
    return jsonify(access_token=access_token), 200

class PrivateResource(Resource):
    @app.route('/protected', methods=['GET'])
    @jwt_required

    def sendData():
        data = get_jwt_identity()
        return mysqldb.addUser("{}".format(str(data['first_name'])),"{}".format(str(data['last_name'])))

if __name__ == '__main__':
    app.run(debug=True)

这个 addUser 功能如下：

def addUser(Fname,Lname):
    try:
        cursorObject = connection.cursor()
        cursorObject.execute("call sp_createUser('{}'".format(Fname)+",'{}')".format(Lname))
        connection.commit()
        connection.close()

    finally:
        print('User data added succesfully!')

我的代码中有什么错误导致了错误？