Use RuntimeError, not AssertionError when guarding against direct View.queryset…

Use RuntimeError, not AssertionError when guarding against direct View.queryset evalutation. Refs #3180.

rest_framework/views.py

@@ -121,7 +121,7 @@ class APIView(View):
         """
         if isinstance(getattr(cls, 'queryset', None), models.query.QuerySet):
             def force_evaluation():
-                raise AssertionError(
+                raise RuntimeError(
                     'Do not evaluate the `.queryset` attribute directly, '
                     'as the result will be cached and reused between requests. '
                     'Use `.all()` or call `.get_queryset()` instead.'

tests/test_generics.py

@@ -541,5 +541,5 @@ class TestGuardedQueryset(TestCase):
 
         view = QuerysetAccessError.as_view()
         request = factory.get('/')
-        with pytest.raises(AssertionError):
+        with pytest.raises(RuntimeError):
             view(request).render()