Issue 20567: Revise idle_test/README.txt and some tests to match new advice.

diff --cc Lib/idlelib/idle_test/test_autocomplete.py
Simple merge

diff --cc Lib/idlelib/idle_test/test_autoexpand.py
Simple merge

diff --cc Lib/idlelib/idle_test/test_paragraph.py
Simple merge

diff --cc Lib/idlelib/idle_test/test_percolator.py
Simple merge

diff --cc Lib/idlelib/idle_test/test_redirector.py
index 998fd6528b6cce87ed32a438094cb12e15d02085,eeec3ea34b1780df41f9fc93ced770536c764c6e..df2b6184c42ff5913e6e351b364ed1ca8a36a32f
--- 1/Lib/idlelib/idle_test/test_redirector.py
--- 2/Lib/idlelib/idle_test/test_widgetredir.py
+++ b/Lib/idlelib/idle_test/test_redirector.py
@@@ -48,9 -48,9 +48,10 @@@ class WidgetRedirectorTest(unittest.Tes
  
      @classmethod
      def tearDownClass(cls):
-         cls.tk.destroy()
-         del cls.text, cls.tk
 +        cls.text.destroy()
+         del cls.text
+         cls.root.destroy()
+         del cls.root
  
      def setUp(self):
          self.redir = WidgetRedirector(self.text)
@@@ -114,9 -114,9 +115,8 @@@
          # Ensure that called through redir .dispatch and not through
          # self.text.insert by having mock raise TclError.
          self.func.__init__(TclError())
-         self.assertEqual(self.tk.call(self.text._w, 'insert', 'boo'), '')
- 
+         self.assertEqual(self.root.call(self.text._w, 'insert', 'boo'), '')
  
  
 -
  if __name__ == '__main__':
      unittest.main(verbosity=2)

diff --cc Lib/idlelib/idle_test/test_replace.py
Simple merge

diff --cc Lib/idlelib/idle_test/test_textview.py
Simple merge

diff --cc Lib/idlelib/idle_test/test_undo.py
Simple merge