Issue #11571: Ensure that the turtle window becomes the topmost window
when launched on Mac OS X.  (Patch by Ronald Oussoren)

diff --git a/Lib/turtle.py b/Lib/turtle.py
--- a/Lib/turtle.py
+++ b/Lib/turtle.py
@@ -110,6 +110,7 @@
 import time
 import os
 import inspect
+import sys
 
 from os.path import isfile, split, join
 from copy import deepcopy
@@ -994,6 +995,13 @@
         self._keys = []
         self.clear()
 
+        if sys.platform == 'darwin':
+            # Force Turtle window to the front on OSX. This is needed
+            # because the Turtle window will show behind the Terminal
+            # window when you show the turtle window from the command-line.
+            cv._rootwindow.call('wm', 'attributes', '.', '-topmost', '1')
+            cv._rootwindow.call('wm', 'attributes', '.', '-topmost', '0')
+
     def clear(self):
         """Delete all drawings and all turtles from the TurtleScreen.