diff -r 180f5bf7d1b9 Lib/tkinter/__init__.py
--- a/Lib/tkinter/__init__.py	Thu Sep 11 14:33:02 2014 +0300
+++ b/Lib/tkinter/__init__.py	Thu Sep 11 16:11:36 2014 +0300
@@ -1921,7 +1921,7 @@ class Tk(Misc, Wm):
     def report_callback_exception(self, exc, val, tb):
         """Internal function. It reports exception on sys.stderr."""
         import traceback
-        sys.stderr.write("Exception in Tkinter callback\n")
+        print("Exception in Tkinter callback", file=sys.stderr)
         sys.last_type = exc
         sys.last_value = val
         sys.last_traceback = tb