I am using python 3.4, Django 1.7.1 (the version considered in the book), Postgres 9.3 and my IDE is Eclipse.
I have been studying the book \"Lightweight Django - Elman
Read the DRF docs here.
In version 2.x a serializer class could sometimes automatically determine the queryset argument if a ModelSerializer class was being used.
This behavior is now replaced with always using an explicit queryset argument for writable relational fields.
You are just using a newer version of DRF than the authors of the code used, so you'll need to either use a lower version or fix the code.
In serializers.py there's this line:
assigned = serializers.SlugRelatedField(slug_field=User.USERNAME_FIELD, required=False)
You need to either add read_only=True
or queryset=User.objects.all()