Custom request on "src" attributes

I implemented a small GrapesJS editor that allows to edit Django/Jinja2 templates. GrapesJS by default is trying to GET the image preview of my element: <a href="{{producturl}}" target="blank"><img src="{{imageurl}}" width="130"/></a> The request happens everytime I load the template into the GrapesJS editor: http://localhost:8000/%7B%7Bimageurl%7D%7D 404 (Not Found) GrapesJS editor though works fine even with this 404 call. But I would like to do handle the request to the image. So instead of GrapesJS making a default call to http://localhost:8000/%7B%7Bimage_url%7D%7D I would like to render...