only in patch2:
unchanged:
--- a/core/modules/file/migration_templates/d7_file_private.yml
+++ b/core/modules/file/migration_templates/d7_file_private.yml
@@ -11,6 +11,7 @@ source:
     # table are specified, and must end with a /. See source_full_path
     # configuration in this migration's process pipeline as an example.
     source_base_path: ''
+  source_module: file
 process:
   # If you are using this file to build a custom migration consider removing
   # the fid field to allow incremental migrations.