Fixed #24701 -- Converted model manager names to unicode in migrations

Thanks to Reto Aebersold for reporting the issue and Tim Graham and
Claude Paroz for the review.

django/db/migrations/state.py

@@ -436,7 +436,7 @@ def flatten_bases(model):
             bases = (models.Model,)
 
         # Constructs all managers on the model
-        managers = {}
+        managers_mapping = {}
 
         def reconstruct_manager(mgr):
             as_manager, manager_path, qs_path, args, kwargs = mgr.deconstruct()
@@ -448,16 +448,17 @@ def reconstruct_manager(mgr):
                 instance = manager_class(*args, **kwargs)
             # We rely on the ordering of the creation_counter of the original
             # instance
-            managers[mgr.name] = (mgr.creation_counter, instance)
+            name = force_text(mgr.name)
+            managers_mapping[name] = (mgr.creation_counter, instance)
 
         if hasattr(model, "_default_manager"):
-            default_manager_name = model._default_manager.name
+            default_manager_name = force_text(model._default_manager.name)
             # Make sure the default manager is always the first
             if model._default_manager.use_in_migrations:
                 reconstruct_manager(model._default_manager)
             else:
                 # Force this manager to be the first and thus default
-                managers[default_manager_name] = (0, models.Manager())
+                managers_mapping[default_manager_name] = (0, models.Manager())
             # Sort all managers by their creation counter
             for _, manager, _ in sorted(model._meta.managers):
                 if manager.name == "_base_manager" or not manager.use_in_migrations:
@@ -467,7 +468,7 @@ def reconstruct_manager(mgr):
             # instance for further processing
             managers = [
                 (name, instance) for name, (cc, instance) in
-                sorted(managers.items(), key=lambda v: v[1])
+                sorted(managers_mapping.items(), key=lambda v: v[1])
             ]
             if managers == [(default_manager_name, models.Manager())]:
                 managers = []
@@ -513,6 +514,7 @@ def construct_managers(self):
         # Sort all managers by their creation counter
         sorted_managers = sorted(self.managers, key=lambda v: v[1].creation_counter)
         for mgr_name, manager in sorted_managers:
+            mgr_name = force_text(mgr_name)
             as_manager, manager_path, qs_path, args, kwargs = manager.deconstruct()
             if as_manager:
                 qs_class = import_string(qs_path)

docs/releases/1.8.1.txt

@@ -66,6 +66,9 @@ Bugfixes
 * Fixed a migration crash when adding new relations to models
   (:ticket:`24573`).
 
+* Fixed a migration crash when applying migrations with model managers on
+  Python 3 that were generated on Python 2 (:ticket:`24701`).
+
 Optimizations
 =============
 

tests/migrations/test_state.py

@@ -7,6 +7,7 @@
     InvalidBasesError, ModelState, ProjectState, get_related_models_recursive,
 )
 from django.test import SimpleTestCase, TestCase, override_settings
+from django.utils import six
 
 from .models import (
     FoodManager, FoodQuerySet, ModelWithCustomBase, NoMigrationFoodManager,
@@ -144,6 +145,7 @@ class Meta:
 
         # The default manager is used in migrations
         self.assertEqual([name for name, mgr in food_state.managers], ['food_mgr'])
+        self.assertTrue(all(isinstance(name, six.text_type) for name, mgr in food_state.managers))
         self.assertEqual(food_state.managers[0][1].args, ('a', 'b', 1, 2))
 
         # No explicit managers defined. Migrations will fall back to the default
@@ -153,11 +155,13 @@ class Meta:
         # default
         self.assertEqual([name for name, mgr in food_no_default_manager_state.managers],
                          ['food_no_mgr', 'food_mgr'])
+        self.assertTrue(all(isinstance(name, six.text_type) for name, mgr in food_no_default_manager_state.managers))
         self.assertEqual(food_no_default_manager_state.managers[0][1].__class__, models.Manager)
         self.assertIsInstance(food_no_default_manager_state.managers[1][1], FoodManager)
 
         self.assertEqual([name for name, mgr in food_order_manager_state.managers],
                          ['food_mgr1', 'food_mgr2'])
+        self.assertTrue(all(isinstance(name, six.text_type) for name, mgr in food_order_manager_state.managers))
         self.assertEqual([mgr.args for name, mgr in food_order_manager_state.managers],
                          [('a', 'b', 1, 2), ('x', 'y', 3, 4)])
 
@@ -220,7 +224,7 @@ def test_render(self):
                 # The ordering we really want is objects, mgr1, mgr2
                 ('default', base_mgr),
                 ('food_mgr2', mgr2),
-                ('food_mgr1', mgr1),
+                (b'food_mgr1', mgr1),
             ]
         ))
 
@@ -234,6 +238,7 @@ def test_render(self):
         managers = sorted(Food._meta.managers)
         self.assertEqual([mgr.name for _, mgr, _ in managers],
                          ['default', 'food_mgr1', 'food_mgr2'])
+        self.assertTrue(all(isinstance(mgr.name, six.text_type) for _, mgr, _ in managers))
         self.assertEqual([mgr.__class__ for _, mgr, _ in managers],
                          [models.Manager, FoodManager, FoodManager])
         self.assertIs(managers[0][1], Food._default_manager)