Python Flask:Mongoengine导入错误：没有名为json的模块

我正在学习mongo教程

我进入了配置MongoEngine和Flask的部分，用以下代码替换旧的init.py：

from flask import Flask
from flask.ext.mongoengine import MongoEngine

app = Flask(__name__)
app.config["MONGODB_SETTINGS"] = {'DB': "my_tumble_log"}
app.config["SECRET_KEY"] = "KeepThisS3cr3t"

db = MongoEngine(app)

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

但现在，当我尝试python manage.py runserver时，出现以下错误：

Traceback (most recent call last):
 File "manage.py", line 6, in <module>
    from tumbleblog import app
  File "/Users/<ME>/tumbleblog/__init__.py", line 2, in <module>
    from flask.ext.mongoengine import MongoEngine
  File "/Users/<ME>/myproject/lib/python2.7/site-packages/flask_mongoengine/__init__.py", line 13,       in <module>
    from .json import overide_json_encoder
  File "/Users/<ME>/myproject/lib/python2.7/site-packages/flask_mongoengine/json.py", line 1, in <module>
    from flask.json import JSONEncoder
ImportError: No module named json

下面是皮普·弗雷泽：

Flask==0.9
Flask-Script==2.0.5
Flask-WTF==0.10.3
Jinja2==2.6
WTForms==2.0.1
Werkzeug==0.8.3
bottle==0.12.8
bson==0.3.3
distribute==0.6.15
flask-mongoengine==0.7.1
gnureadline==6.3.3
gunicorn==0.17.2
ipython==2.1.0
lxml==3.4.0
mongoengine==0.8.7
pymongo==2.7.2
pypm==1.3.4
pythonselect==1.3
pytz==2014.10
requests==2.2.1
stevedore==0.15
virtualenv==1.6.1
virtualenv-clone==0.2.5
virtualenvwrapper==4.2
wsgiref==0.1.2

---

有什么问题吗？看来我所有的mongo软件都是最新的。

您需要将Flask升级到0.10或安装Flask wtf的旧版本（0.8.4）

资料来源：

---

您需要将Flask升级到0.10或安装旧版本（0.8.4）的Flask wtf

资料来源：

---

您需要将Flask升级到0.10或安装旧版本（0.8.4）的Flask wtf

资料来源：

---

您需要将Flask升级到0.10或安装旧版本（0.8.4）的Flask wtf

资料来源：

Flask==0.9
Flask-Script==2.0.5
Flask-WTF==0.10.3
Jinja2==2.6
WTForms==2.0.1
Werkzeug==0.8.3
bottle==0.12.8
bson==0.3.3
distribute==0.6.15
flask-mongoengine==0.7.1
gnureadline==6.3.3
gunicorn==0.17.2
ipython==2.1.0
lxml==3.4.0
mongoengine==0.8.7
pymongo==2.7.2
pypm==1.3.4
pythonselect==1.3
pytz==2014.10
requests==2.2.1
stevedore==0.15
virtualenv==1.6.1
virtualenv-clone==0.2.5
virtualenvwrapper==4.2
wsgiref==0.1.2