diff -r b40025e37bcd Lib/idlelib/PyShell.py
--- a/Lib/idlelib/PyShell.py	Wed Oct 03 03:18:33 2012 +0200
+++ b/Lib/idlelib/PyShell.py	Wed Oct 03 17:09:48 2012 -0500
@@ -1295,7 +1295,8 @@
        idle  [-dns] [-t title] - [arg]*
 
   -h         print this help message and exit
-  -n         run IDLE without a subprocess (see Help/IDLE Help for details)
+  -n         run IDLE without a subprocess (DEPRECATED,
+             see Help/IDLE Help for details)
 
 The following options will override the IDLE 'settings' configuration:
 
@@ -1373,6 +1374,8 @@
         if o == '-i':
             enable_shell = True
         if o == '-n':
+            print(" Warning: running IDLE without a subprocess is deprecated.",
+                  file=sys.stderr)
             use_subprocess = False
         if o == '-r':
             script = a
diff -r b40025e37bcd Lib/idlelib/help.txt
--- a/Lib/idlelib/help.txt	Wed Oct 03 03:18:33 2012 +0200
+++ b/Lib/idlelib/help.txt	Wed Oct 03 17:09:48 2012 -0500
@@ -256,7 +256,7 @@
 
 	Enter idle -h at the command prompt to get a usage message.
 
-Running without a subprocess:
+Running without a subprocess: (DEPRECATED)
 
 	If IDLE is started with the -n command line switch it will run in a
 	single process and will not create the subprocess which runs the RPC