Fixed #21014 -- Fixed gobbled ImportError in MigrationLoader.

django/db/migrations/loader.py

@@ -63,6 +63,7 @@ class MigrationLoader(object):
                 if "No module named" in str(e) and "migrations" in str(e):
                     self.unmigrated_apps.add(app_label)
                     continue
+                raise
             self.migrated_apps.add(app_label)
             directory = os.path.dirname(module.__file__)
             # Scan for .py[c|o] files

tests/migrations/faulty_migrations/import_error/__init__.py

@@ -0,0 +1 @@
+import fake_python_module

tests/migrations/test_loader.py

@@ -77,3 +77,10 @@ class LoaderTests(TestCase):
             migration_loader.get_migration_by_prefix("migrations", "0")
         with self.assertRaises(KeyError):
             migration_loader.get_migration_by_prefix("migrations", "blarg")
+
+    def test_load_import_error(self):
+        migration_loader = MigrationLoader(connection)
+
+        with override_settings(MIGRATION_MODULES={"migrations": "migrations.faulty_migrations.import_error"}):
+            with self.assertRaises(ImportError):
+                migration_loader.load_disk()