diff -r 135e1a8144ec Lib/test/test_readline.py
--- a/Lib/test/test_readline.py	Mon Jan 09 11:21:37 2017 +0100
+++ b/Lib/test/test_readline.py	Mon Jan 09 21:37:24 2017 +0100
@@ -216,7 +216,7 @@
     output = bytearray()
     [master, slave] = pty.openpty()
     args = (sys.executable, '-c', script)
-    proc = subprocess.Popen(args, stdin=slave, stdout=slave, stderr=slave)
+    proc = subprocess.Popen(args, stdin=slave, stdout=slave)
     os.close(slave)
     with ExitStack() as cleanup:
         cleanup.enter_context(proc)
diff -r 135e1a8144ec Modules/readline.c
--- a/Modules/readline.c	Mon Jan 09 11:21:37 2017 +0100
+++ b/Modules/readline.c	Mon Jan 09 21:37:24 2017 +0100
@@ -1188,6 +1188,7 @@
 rlhandler(char *text)
 {
     completed_input_string = text;
+    fprintf(stderr, "\nchar *text: \"%s\"\n", text);
     rl_callback_handler_remove();
 }