from django.db import models

class Collection(models.Model):
    name = models.CharField(max_length=50)
    prod_category = models.CharField(max_length=50)
    description = models.TextField()
    manufacturer = models.TextField()
    num_products = models.IntegerField()
    image_url = models.URLField()

from oscar.apps.catalogue.abstract_models import AbstractProduct

class Product(AbstractProduct):
    collection = models.ForeignKey(Collection, on_delete=models.CASCADE)
    multiplier = models.DecimalField(max_digits=2, decimal_places=1)

from oscar.apps.catalogue.models import *

Running migrations:
  Applying catalogue.0014_auto_20181211_1617...Traceback (most recent call last):
  File "/home/mysite/lib/python3.7/Django-2.1.3-py3.7.egg/django/db/backends/utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
psycopg2.IntegrityError: insert or update on table "catalogue_product" violates foreign key constraint "catalogue_product_collection_id_e8789e0b_fk_catalogue"
DETAIL:  Key (collection_id)=(1) is not present in table "catalogue_collection".