《Flask Web开发》学习笔记之bug--（9）【jinja2.exceptions.TemplateSyntaxError: unexpected '%'】

/app/main/views.py

from flask import render_template, session, redirect, url_for, current_app
from .. import db
from ..models import User
from ..email import send_email
from . import main
from .forms import NameForm


@main.route('/', methods=['GET', 'POST'])
def index():
	form = NameForm()
	if form.validate_on_submit():
		user = User.query.filter_by(username=form.name.data).first()
		if user is None:
			user = User(username=form.name.data)
			db.session.add(user)
			session['known'] = False
			if current_app.config['FLASKY_ADMIN']:
				send_mail(current_app.config['FLASKY_ADMIN'], \
					'New User', 'mail//new_user', user=user)
		else:
			session['known'] = True
		session['name'] = form.name.data
		return redirect(url_for('.index'))
	return render_template('index.html', form=form, name=session.get('name'), known=session.get('known', False))

/app/templates/base.html

{% extends "bootstrap/base.html" %}

{% block title %}Flasky{% endblock %}

{% block head %}
{
  
  { super() }}
<link rel="shortcut icon" href="{
  
  { url_for('static', filename='favicon.ico') }}" type="image/x-icon">
<link rel="icon" href="{
  
  { url_for('static', filename='favicon.ico') }}" type="image/x-icon">
{% endblock %}

{% block navbar %}
<div class="navbar navbar-inverse" role="navigation">
	<div class="container">
		<div class="navbar-header">
			<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-toggle">
				<span class="sr-only">Toggle navigation</span>
				<span class="icon-bar"></span>
				<span class="icon-bar"></span>
				<span class="icon-bar"></span>
			</button>
			<a class="navbar-brand" href="{
  
  { url_for('main.index') }}">Flask</a>
		</div>
		<div class="navbar-collapse collapse">
			<ul class="nav navbar-nav navbar-right">
				{% if current_user.is_authenticated() %}
				<li><a href="{
  
  { url_for('auth.logout') }}">Sign Out</a></li>
				{% else %}
				<li><a href="{
  
  { url_for('auth.login') }}">Sign In</a></li>
				{% endif %}
			</ul>
		</div>
	</div>
</div>
{% endblock %}

{% block content %}
<div class="container">
	{% for message in get_flashed_messages() %}
	<div class="alert alert-warning">
		<button type="button" class="close" data-dismiss="alert">×</button>
		{
  
  { message }}
	</div>
	{
  
  {% endfor %}}

	{% block page_content %}{% endblock %}
</div>
{% endblock %}

{% block scripts %}
{
  
  { super() }}
{
  
  { moment.include_moment() }}
{% endblock %}

报错信息：

$ python3 manage.py runserver --host 0.0.0.0
/home/henry/.local/lib/python3.5/site-packages/flask_sqlalchemy/__init__.py:800: UserWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True to suppress this warning.
  warnings.warn('SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True to suppress this warning.')
 * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
 * Restarting with stat
/home/henry/.local/lib/python3.5/site-packages/flask_sqlalchemy/__init__.py:800: UserWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True to suppress this warning.
  warnings.warn('SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the fu