How to make a contact form in Django?

Question

Django

There is a contact form on every page of the website. It is created through the inclusion_tag. But how to process it?
First I did it in the same inclusion_tag, but I found out that it cannot redirect to the page with the inscription - sent successfully, because cannot return a Response.
The second idea is to make the action of the form tag on the url - /mail. And there in the view to process it.
The question is. If is_valid returns false, how do I go back to the old page and print errors to the form?