NameError: global name 'render_template' is not defined（关键词：flask/bug）

项目结构：

/home/henry/dev/flask_henry
hello.py  hello.pyc  README.md  templates  venv_flask_henry

hello.py代码：

from flask import Flask
from flask_script import Manager

app = Flask(__name__)

manager = Manager(app)

@app.route('/')
def index():
    return render_template('index.html')

@app.route('/user/<name>')
def user(name):
    return render_template('user.html', name=name)

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

报错：

(venv_flask_henry) henry@henry-virtual-machine:~/dev/flask_henry$ python hello.py runserver --host 0.0.0.0
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
[2017-11-26 14:11:30,844] ERROR in app: Exception on /user/HeLi [GET]
Traceback (most recent call last):
  File "/home/henry/dev/flask_henry/venv_flask_henry/local/lib/python2.7/site-packages/flask/app.py", line 1982, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/henry/dev/flask_henry/venv_flask_henry/local/lib/python2.7/site-packages/flask/app.py", line 1614, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/henry/dev/flask_henry/venv_flask_henry/local/lib/python2.7/site-packages/flask/app.py", line 1517, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/henry/dev/flask_henry/venv_flask_henry/local/lib/python2.7/site-packages/flask/app.py", line 1612, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/henry/dev/flask_henry/venv_flask_henry/local/lib/python2.7/site-packages/flask/app.py", line 1598, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "hello.py", line 14, in user
    return render_template('user.html', name=name)
NameError: global name 'render_template' is not defined
127.0.0.1 - - [26/Nov/2017 14:11:30] "GET /user/HeLi HTTP/1.1" 500 -

注意到这一行：
NameError: global name ‘render_template’ is not defined

原因是：
hello.py中没有导入render_template

补上

from flask import render_template

即可。