I really like the new path method so I decided to check out Django 2.0. Among the new feature there are some minor changes such as with the ForeignKey field.ForeignKey is a Django field for defining a many-to-one relationship.
Up until Django 1.9 the ForeignKey field required a single argument: the model to map to.
Since Django 2.0 the ForeignKey field requires two positional arguments:
the model to map to
the on_delete argument
For a quick fix you can find the instruction in the video.