Fix add_roles_for_object_creator handling of AnonymousUser

Author: gerrod3

CHANGES/plugin_api/+anon-user-object-create.bugfix

@@ -0,0 +1 @@
+Fixed `add_roles_for_object_creator` not handling anonymous users.

pulpcore/app/models/access_policy.py

@@ -140,7 +140,7 @@ def add_roles_for_object_creator(self, roles):
 
         roles = _ensure_iterable(roles)
         current_user = get_current_authenticated_user()
-        if current_user:
+        if current_user and isinstance(current_user, get_user_model()):
             for role in roles:
                 assign_role(role, current_user, self)