[Answered ]-Error while outputting template engine maximum recursion depth exceeded while calling a Python object

Your index.html template includes the sales.html template, and the sales.html template extends the index.html template. As a result if you render index.html or sale.html, it will get stuck in an infinite loop.

You can remove the {% include 'article/sales.html' %} part of the index.html page. The fact that you defined a block that can be filled in by the sales.html template is sufficient.