Fixed #23618 -- Allowed apps with no models to still have migrations

Basically a4737bf6 reapplied.

django/db/migrations/loader.py

@@ -63,8 +63,6 @@ class MigrationLoader(object):
         self.unmigrated_apps = set()
         self.migrated_apps = set()
         for app_config in apps.get_app_configs():
-            if app_config.models_module is None:
-                continue
             # Get the migrations module directory
             module_name = self.migrations_module(app_config.label)
             was_loaded = module_name in sys.modules

docs/releases/1.8.txt

@@ -276,6 +276,9 @@ Migrations
 * The :class:`~django.db.migrations.operations.RunSQL` operation can now handle
   parameters passed to the SQL statements.
 
+* It is now possible to have migrations (most probably :ref:`data migrations
+  <data-migrations>`) for applications without models.
+
 Models
 ^^^^^^