User.has_perm should forward **kwargs to allow more flexibility in authentication backends

[Matteo Parrucci]

The situation
I would like to check user permission based on the django.contrib.sites I'm in. To get the active site, django.contrib.sites needs the request so he can match the hostname. I'm using django-rules at the moment but It's quite generic.

The Problem
Not having the request in has_perm/has_perms I cannot check permissions based on the currently active site
The "call stack" detail is here: ​https://github.com/dfunckt/django-rules/issues/130

A possible solution
Adding **kwargs to has_perm and has_perms signatures would allow greater flexibility for the custom authentication backends leaving intact what we have now. In my case, for example, I could check permission in my django-rules predicates having the the request passed in and check if I have rights for the current site, but I think my case is quite limited and all new authentication backends would benefit from this change.