Enable FSpResourceFileAlreadyOpen only for Carbon. This is not strictly correct: OS9 InterfaceLib has it, but enabling it will make Python refuse to run on 8.6 and earlier.
diff --git a/Mac/Modules/res/resscan.py b/Mac/Modules/res/resscan.py
index 4b1babc..544e303 100644
--- a/Mac/Modules/res/resscan.py
+++ b/Mac/Modules/res/resscan.py
@@ -63,6 +63,7 @@
 				'FSpOpenOrphanResFile',
 				'DetachResourceFile',
 				'InsertResourceFile',
+				'FSpResourceFileAlreadyOpen',
 			])]
 
 	def makerepairinstructions(self):