admindocs crash if a Feed is configured

[Paul Donohue]

If a Feed (​https://docs.djangoproject.com/en/2.0/ref/contrib/syndication/) is configured anywhere in the project, then /admin/doc/views/ (​https://docs.djangoproject.com/en/2.0/ref/contrib/admin/admindocs/) crashes with AttributeError: 'GlobalFeed' object has no attribute '__qualname__'

The problem is that Feed is a callable object (​https://github.com/django/django/blob/master/django/contrib/syndication/views.py#L34) and the documentation uses that class directly as a View (path('latest/feed/', LatestEntriesFeed()),), but admindocs assumes that all views are functions and it does not work properly with a callable object (​https://github.com/django/django/blob/master/django/contrib/admindocs/views.py#L130).

In Django 1.11 and earlier, admindocs supported callable objects on Python 2 because it used view.__name__ instead of view.__qualname__, but it appears that the Python 3 code in admindocs has not supported this since it was added in ​https://github.com/django/django/commit/ae0f55eb491255217d6df31296ec8102007224a6 (https://code.djangoproject.com/ticket/27018).

As a work-around, __qualname__ can be manually defined on Feed objects:

class MyFeed(Feed):
    def __init__(self):
        super().__init__()
        self.__qualname__ = '__call__'

Without knowing Django's opinion of the use of callable objects as views, I don't know the appropriate way to fix this: Should admindocs support callable objects as views, or should Feed not use a callable object as a view?