Django: Context processors for error pages (or request in simple_tag)
For those who may step on the same rakes: 
What I ended up doing is passing the "app_name" variable from the error page views to the context. Thus the variable is in the context for non-error pages, because it is set by the context processor, and it is there for error pages because it is passed manually. Doesn't look like a good solution though.
In my Django project, there are several django apps. I want to write custom error pages, and I want them to contain correct links to the application that the errors happened in, for example, if a 500-error happened in my app a, I want the error page contain a link to /a/index.html, and if a server error happened in app b, I want the page to contain the link to /b/index.html. And I want to create only one copy of each of the error page files, which means I need to get the name of the app from within the template.
To that end, I have written a custom context processor that adds the app_name var to the templates. I tested it on my normal pages, but when I went on to test it on the error pages, turns out that the context processor isn't firing. 
Similarly, I have written a template tag app_aware_url which takes the name of the url pattern and tries to resolve it, but again, turns out that for the error pages the simple_tag(takes_context=True) receives a context that does not contain the request (which is needed for telling which app I am in).
Is there a way round it, or is there a better solution to my problem altogether?
(Django is 1.11)