Fixed #21015 -- Fixed MigrationLoader when importlib.import_module returns a file module or an empty directory.

django/db/migrations/loader.py

@@ -64,6 +64,13 @@ class MigrationLoader(object):
                     self.unmigrated_apps.add(app_label)
                     continue
                 raise
+            else:
+                # PY3 will happily import empty dirs as namespaces.
+                if not hasattr(module, '__file__'):
+                    continue
+                # Module is not a package (e.g. migrations.py).
+                if not hasattr(module, '__path__'):
+                    continue
             self.migrated_apps.add(app_label)
             directory = os.path.dirname(module.__file__)
             # Scan for .py[c|o] files

tests/migrations/test_loader.py

@@ -1,8 +1,11 @@
+from unittest import skipIf
+
 from django.test import TestCase
 from django.test.utils import override_settings
 from django.db import connection
 from django.db.migrations.loader import MigrationLoader, AmbiguityError
 from django.db.migrations.recorder import MigrationRecorder
+from django.utils import six
 
 
 class RecorderTests(TestCase):
@@ -84,3 +87,16 @@ class LoaderTests(TestCase):
         with override_settings(MIGRATION_MODULES={"migrations": "migrations.faulty_migrations.import_error"}):
             with self.assertRaises(ImportError):
                 migration_loader.load_disk()
+
+    def test_load_module_file(self):
+        migration_loader = MigrationLoader(connection)
+
+        with override_settings(MIGRATION_MODULES={"migrations": "migrations.faulty_migrations.file"}):
+            migration_loader.load_disk()
+
+    @skipIf(six.PY2, "PY2 doesn't load empty dirs.")
+    def test_load_empty_dir(self):
+        migration_loader = MigrationLoader(connection)
+
+        with override_settings(MIGRATION_MODULES={"migrations": "migrations.faulty_migrations.namespace"}):
+            migration_loader.load_disk()