Oops, these compatibility modules were missing. Which went unnoticed because their companions had been put in the wrong place.
diff --git a/Mac/Lib/lib-compat/Qdoffs.py b/Mac/Lib/lib-compat/Qdoffs.py
new file mode 100644
index 0000000..4f7744c
--- /dev/null
+++ b/Mac/Lib/lib-compat/Qdoffs.py
@@ -0,0 +1 @@
+from Carbon.Qdoffs import *