moved fix tree to apps ready hook and wrapped in catch for non existing models

cookbook/apps.py

@@ -1,5 +1,7 @@
 from django.apps import AppConfig
 from django.conf import settings
+from django.db import OperationalError
+from django_scopes import scopes_disabled
 
 
 class CookbookConfig(AppConfig):
@@ -9,3 +11,14 @@ class CookbookConfig(AppConfig):
         # post_save signal is only necessary if using full-text search on postgres
         if settings.DATABASES['default']['ENGINE'] in ['django.db.backends.postgresql_psycopg2', 'django.db.backends.postgresql']:
             import cookbook.signals  # noqa
+
+        # when starting up run fix_tree to:
+        #   a) make sure that nodes are sorted when switching between sort modes
+        #   b) fix problems, if any, with tree consistency
+        with scopes_disabled():
+            try:
+                from cookbook.models import Keyword, Food
+                Keyword.fix_tree(fix_paths=True)
+                Food.fix_tree(fix_paths=True)
+            except OperationalError:
+                pass # if model does not exist there is no need to fix it

cookbook/models.py

@@ -358,13 +358,6 @@ class Keyword(ExportModelOperationsMixin('keyword'), TreeModel, PermissionModelM
         indexes = (Index(fields=['id', 'name']),)
 
 
-# when starting up run fix_tree to:
-#   a) make sure that nodes are sorted when switching between sort modes
-#   b) fix problems, if any, with tree consistency
-with scopes_disabled():
-    Keyword.fix_tree(fix_paths=True)
-
-
 class Unit(ExportModelOperationsMixin('unit'), models.Model, PermissionModelMixin):
     name = models.CharField(max_length=128, validators=[MinLengthValidator(1)])
     description = models.TextField(blank=True, null=True)
@@ -412,13 +405,6 @@ class Food(ExportModelOperationsMixin('food'), TreeModel, PermissionModelMixin):
         )
 
 
-# when starting up run fix_tree to:
-#   a) make sure that nodes are sorted when switching between sort modes
-#   b) fix problems, if any, with tree consistency
-with scopes_disabled():
-    Food.fix_tree(fix_paths=True)
-
-
 class Ingredient(ExportModelOperationsMixin('ingredient'), models.Model, PermissionModelMixin):
     # a pre-delete signal on Food checks if the Ingredient is part of a Step, if it is raises a ProtectedError instead of cascading the delete
     food = models.ForeignKey(Food, on_delete=models.CASCADE, null=True, blank=True)