move import to the right file :)

shop/admin.py

@@ -1,4 +1,4 @@
-from django.contrib import admin, messages
+from django.contrib import admin
 
 from . import models
 

shop/models.py

@@ -1,6 +1,7 @@
 from django.conf import settings
 from django.db import models
 from django.db.models.aggregates import Sum
+from django.contrib import messages
 from django.contrib.postgres.fields import DateTimeRangeField, JSONField
 from django.http import HttpResponse
 from django.utils.text import slugify