/dev/ptmx doesn't exist on AIX, they had to be different and use /dev/ptc.
Otherwise, the 2 devices seem to work the same for allocating a pseudo-tty.
diff --git a/pyconfig.h.in b/pyconfig.h.in
index 37fd5fc..e0ab1b9 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -68,6 +68,9 @@
 /* Define to 1 if you have the device macros. */
 #undef HAVE_DEVICE_MACROS
 
+/* Define if we have /dev/ptc. */
+#undef HAVE_DEV_PTC
+
 /* Define if we have /dev/ptmx. */
 #undef HAVE_DEV_PTMX