Fix person_required with support for anonymous users (3. try)

Addition to MR #110

aleksis/core/decorators.py

 from typing import Callable
 
 from django.contrib.auth.decorators import login_required, user_passes_test
-
-from aleksis.core.util.core_helpers import has_person
+from django.contrib.auth.models import User
 
 
 def admin_required(function: Callable = None) -> Callable:
@@ -10,8 +9,12 @@ def admin_required(function: Callable = None) -> Callable:
     return actual_decorator(function)
 
 
+def has_person_by_user(user: User) -> bool:
+    return getattr(user, "person", None) is not None
+
+
 def person_required(function: Callable = None) -> Callable:
     """ Requires a logged-in user which is linked to a person. """
 
-    actual_decorator = user_passes_test(has_person)
+    actual_decorator = user_passes_test(has_person_by_user)
     return actual_decorator(login_required(function))