At Tim Peters' recommendation, add a dummy flush() method to PseudoFile.
diff --git a/Tools/idle/ScriptBinding.py b/Tools/idle/ScriptBinding.py
index 0e7810b..a1a7f2c 100644
--- a/Tools/idle/ScriptBinding.py
+++ b/Tools/idle/ScriptBinding.py
@@ -70,6 +70,9 @@
     def writelines(self, l):
         map(self.write, l)
 
+    def flush(self):
+        pass
+
 
 class ScriptBinding: