Wiki integration. Requests don't always have sessions. In particular this occurs when a request is made without a trailing slash. The Common middleware redirects when this happens, and the middleware process_request() processing stops before a session can get added. So just set an attribute on the request object for each operation. This seemed weird to me at first, but there are plenty of examples of this in the Django code base already.

from django.contrib import admin
from django.contrib.flatpages.models import FlatPage
from django.contrib.flatpages.admin import FlatPageAdmin as FlatPageAdminOld
from django.conf import settings

class FlatPageAdmin(FlatPageAdminOld):
    class Media:
        js = settings.GPP_THIRD_PARTY_JS['tiny_mce']

# We have to unregister it, and then reregister
admin.site.unregister(FlatPage)
admin.site.register(FlatPage, FlatPageAdmin)