Issue #11918: OS/2 and VMS are no more supported because of the lack of
maintainer.
diff --git a/Modules/main.c b/Modules/main.c
index 9137c85..747c12f 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -6,6 +6,7 @@
 #include <locale.h>
 
 #ifdef __VMS
+#error "PEP 11: VMS is now unsupported, code will be removed in Python 3.4"
 #include <unixlib.h>
 #endif
 
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 2eb3e92..396243e 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -30,6 +30,7 @@
 #include "Python.h"
 
 #if defined(__VMS)
+#    error "PEP 11: VMS is now unsupported, code will be removed in Python 3.4"
 #    include <unixio.h>
 #endif /* defined(__VMS) */
 
@@ -45,6 +46,7 @@
 
 
 #if defined(PYOS_OS2)
+#error "PEP 11: OS/2 is now unsupported, code will be removed in Python 3.4"
 #define  INCL_DOS
 #define  INCL_DOSERRORS
 #define  INCL_DOSPROCESS