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/Resmodule.c b/Mac/Modules/res/Resmodule.c
index 42c8800..bd6a42d 100644
--- a/Mac/Modules/res/Resmodule.c
+++ b/Mac/Modules/res/Resmodule.c
@@ -1353,6 +1353,8 @@
 }
 #endif
 
+#if TARGET_API_MAC_CARBON
+
 static PyObject *Res_FSpResourceFileAlreadyOpen(_self, _args)
 	PyObject *_self;
 	PyObject *_args;
@@ -1378,6 +1380,7 @@
 	                     refNum);
 	return _res;
 }
+#endif
 
 #if TARGET_API_MAC_CARBON
 
@@ -1600,8 +1603,11 @@
 	{"DetachResourceFile", (PyCFunction)Res_DetachResourceFile, 1,
 	 "(SInt16 refNum) -> (OSErr _rv)"},
 #endif
+
+#if TARGET_API_MAC_CARBON
 	{"FSpResourceFileAlreadyOpen", (PyCFunction)Res_FSpResourceFileAlreadyOpen, 1,
 	 "(FSSpec resourceFile) -> (Boolean _rv, Boolean inChain, SInt16 refNum)"},
+#endif
 
 #if TARGET_API_MAC_CARBON
 	{"FSpOpenOrphanResFile", (PyCFunction)Res_FSpOpenOrphanResFile, 1,
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):