Issue #27365: partial merge

diff --cc Lib/idlelib/idle_test/test_textview.py
index 764a1a5e1b010c0ec89e69691248fc602a5e1d5b,02d1472240ee0c4e3c5db667786bd2fe06374814..0c625eefe9031030a5e9fa9d488ebfeb17626c89
--- 1/Lib/idlelib/idle_test/test_textview.py
--- 2/Lib/idlelib/idle_test/test_textview.py
+++ b/Lib/idlelib/idle_test/test_textview.py
@@@ -5,17 -5,17 +5,17 @@@ is a widget containing multiple widgets
  Using mock Text would not change this.  Other mocks are used to retrieve
  information about calls.
  
--The coverage is essentially 100%.
++Coverage: 94%.
  '''
 +from idlelib import textview as tv
  from test.support import requires
  requires('gui')
  
  import unittest
  import os
  from tkinter import Tk
 -from idlelib import textView as tv
  from idlelib.idle_test.mock_idle import Func
--from idlelib.idle_test.mock_tk import Mbox
++from idlelib.idle_test.mock_tk import Mbox_func
  
  def setUpModule():
      global root
@@@ -64,17 -64,17 +64,17 @@@ class TextViewTest(unittest.TestCase)
          view.destroy
  
  
--class textviewTest(unittest.TestCase):
++class ViewFunctionTest(unittest.TestCase):
  
      @classmethod
      def setUpClass(cls):
--        cls.orig_mbox = tv.tkMessageBox
--        tv.tkMessageBox = Mbox
++        cls.orig_error = tv.showerror
++        tv.showerror = Mbox_func()
  
      @classmethod
      def tearDownClass(cls):
--        tv.tkMessageBox = cls.orig_mbox
--        del cls.orig_mbox
++        tv.showerror = cls.orig_error
++        del cls.orig_error
  
      def test_view_text(self):
          # If modal True, tkinter will error with 'can't invoke "event" command'
@@@ -89,7 -89,7 +89,7 @@@
          self.assertIn('Test', view.textView.get('1.0', '1.end'))
          view.Ok()
  
--        # Mock messagebox will be used and view_file will not return anything
++        # Mock showerror will be used and view_file will return None
          testfile = os.path.join(test_dir, '../notthere.py')
          view = tv.view_file(root, 'Title', testfile, modal=False)
          self.assertIsNone(view)

diff --cc Lib/idlelib/textView.py
Simple merge