[1.8.x] 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.

Backport of faad6070 from master

django/db/migrations/state.py

@@ -419,7 +419,7 @@ class ModelState(object):
             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()
@@ -431,16 +431,17 @@ class ModelState(object):
                 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:
@@ -450,7 +451,7 @@ class ModelState(object):
             # 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 = []
@@ -496,6 +497,7 @@ class ModelState(object):
         # 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 @@ from django.db.migrations.state import (
     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,
@@ -143,6 +144,7 @@ class StateTests(TestCase):
 
         # 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
@@ -152,11 +154,13 @@ class StateTests(TestCase):
         # 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)])
 
@@ -203,7 +207,7 @@ class StateTests(TestCase):
                 # The ordering we really want is objects, mgr1, mgr2
                 ('default', base_mgr),
                 ('food_mgr2', mgr2),
-                ('food_mgr1', mgr1),
+                (b'food_mgr1', mgr1),
             ]
         ))
 
@@ -217,6 +221,7 @@ class StateTests(TestCase):
         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)