flask报错：“Exception: Unexpected end of template. Jinja was looking for the following tags: ‘endfor’ ”

报错详情：

Exception: Unexpected end of template. Jinja was looking for the following tags: 'endfor' or 'else'. The innermost block that needs to be closed is 'for'.

Exception: Unexpected end of template. Jinja was looking for the following tags: 'endfor' or 'else'. The innermost block that needs to be closed is 'for'.
127.0.0.1 - - [26/Dec/2018 12:29:38] "GET /admin/login/ HTTP/1.1" 302 -

Exception: Unexpected end of template. Jinja was looking for the following tags: 'endfor' or 'else'. The innermost block that needs to be closed is 'for'.
127.0.0.1 - - [26/Dec/2018 12:29:38] "GET /admin/login/ HTTP/1.1" 302 -

报错原因：jinja语句中 “ % ” 和 “ { ” 之间有空格

{% for msg in get_flashed_messages() %}
     <p class="login-box-msg" style="color: red">{{ msg }}</p>
{  % endfor %}

解决方法：去除空格

{% for msg in get_flashed_messages() %}
    <p class="login-box-msg" style="color: red">{{ msg }}</p>
{% endfor %}