新手求教，python中返回json格式出错

本人想实现查询数据库中表goods并用json格式返回所有数据，但是就是出错，求大神解答!

 在这里书写代码片  

# -*- coding:utf-8 -*-

from flask import *
from MySQLdb import *
from json import *
import MySQLdb.cursors
import sys
import json
app = Flask(__name__)

@app.route('/query',methods=['GET','POST'])
def query():
    form=request.form
    cn = Connection(host='localhost',user= 'admin_1',passwd= "11111", db='SecondhandPlatform',
            charset='utf8', cursorclass=MySQLdb.cursors.DictCursor)
    cur = cn.cursor()
    try:
        cur.execute('select * from goods')
        rows = cur.fetchall()
        j_arr = json.dumps(rows,ensure_ascii=False)
        #data = {'success':'true','msg':'fetch data! success', 'result':j_arr}
        #return json.dumps(data)
        return jsonify(success=True,msg=u'Fetch data successfully',result=j_arr)
    except:
        return jsonify(success=False,msg=u'Unable fetch data',result=None)

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