AttributeError 'ChangesModel' object has no attribute 'permissions_field'

[leplatrem]

AttributeError 'ChangesModel' object has no attribute 'permissions_field'
  ...
  File "pyramid/viewderivers.py", line 436, in rendered_view
    result = view(context, request)
  File "pyramid/viewderivers.py", line 144, in _requestonly_view
    response = view(request)
  File "cornice/service.py", line 500, in wrapper
    response = view_()
  File "kinto_changes/views.py", line 90, in plural_get
    result = super().plural_get()
  File "kinto/core/resource/__init__.py", line 337, in plural_get
    return self._plural_get(False)
  File "kinto/core/resource/__init__.py", line 344, in _plural_get
    self._raise_412_if_modified(obj={})
  File "kinto/core/resource/__init__.py", line 989, in _raise_412_if_modified
    existing.pop(self.model.permissions_field, None)
``