[2.2.x] Refs #30179 -- Moved topological sort functions to django.utils.

Backport of e04209e181c99ac16ca769d115ac640015a83757 from master.

2 files changed, 6 insertions, 3 deletions

diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py
index 3d3eeb9230..0dc1c77c53 100644
--- a/django/db/migrations/autodetector.py
+++ b/django/db/migrations/autodetector.py
@@ -12,8 +12,7 @@ from django.db.migrations.questioner import MigrationQuestioner
 from django.db.migrations.utils import (
     COMPILED_REGEX_TYPE, RegexObject, get_migration_name_timestamp,
 )
-
-from .topological_sort import stable_topological_sort
+from django.utils.topological_sort import stable_topological_sort
 
 
 class MigrationAutodetector:
diff --git a/django/db/migrations/topological_sort.py b/django/utils/topological_sort.py
index e0a22c9236..3f8ea0f2e4 100644
--- a/django/db/migrations/topological_sort.py
+++ b/django/utils/topological_sort.py
@@ -1,3 +1,7 @@
+class CyclicDependencyError(ValueError):
+    pass
+
+
 def topological_sort_as_sets(dependency_graph):
     """
     Variation of Kahn's algorithm (1962) that returns sets.
@@ -13,7 +17,7 @@ def topological_sort_as_sets(dependency_graph):
         current = {node for node, deps in todo.items() if not deps}
 
         if not current:
-            raise ValueError('Cyclic dependency in graph: {}'.format(
+            raise CyclicDependencyError('Cyclic dependency in graph: {}'.format(
                 ', '.join(repr(x) for x in todo.items())))
 
         yield current