[Fixed]-TemplateDoesNotExist at /lab/

Solution: Extend base template like this: {% extends 'lab/base.html' %}

Explanation:

If you write just {% extends 'base.html' %}, Django will look for base.html in lab/templates/. But there isn’t any in this directory.

In fact, base.html is inside lab/templates/lab/ directory. That is why, you’ll need to specify the name of app directory which contains the base.html