[3.9] bpo-42630: Improve error reporting in Tkinter for absent default root (GH-23781) (GH-23853)

* Tkinter functions and constructors which need a default root window
  raise now RuntimeError with descriptive message instead of obscure
  AttributeError or NameError if it is not created yet or cannot
  be created automatically.

* Add tests for all functions which use default root window.

* Fix import in the pynche script.

(cherry picked from commit 3d569fd6dc)

Lib/tkinter/test/test_tkinter/test_images.py

@@ -1,7 +1,7 @@
 import unittest
 import tkinter
 from test import support
-from tkinter.test.support import AbstractTkTest, requires_tcl
+from tkinter.test.support import AbstractTkTest, AbstractDefaultRootTest, requires_tcl
 
 support.requires('gui')
 
@@ -19,6 +19,47 @@ class MiscTest(AbstractTkTest, unittest.TestCase):
         self.assertIsInstance(image_names, tuple)
 
 
+class DefaultRootTest(AbstractDefaultRootTest, unittest.TestCase):
+
+    def test_image_types(self):
+        self.assertRaises(RuntimeError, tkinter.image_types)
+        root = tkinter.Tk()
+        image_types = tkinter.image_types()
+        self.assertIsInstance(image_types, tuple)
+        self.assertIn('photo', image_types)
+        self.assertIn('bitmap', image_types)
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.image_types)
+
+    def test_image_names(self):
+        self.assertRaises(RuntimeError, tkinter.image_names)
+        root = tkinter.Tk()
+        image_names = tkinter.image_names()
+        self.assertIsInstance(image_names, tuple)
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.image_names)
+
+    def test_image_create_bitmap(self):
+        self.assertRaises(RuntimeError, tkinter.BitmapImage)
+        root = tkinter.Tk()
+        image = tkinter.BitmapImage()
+        self.assertIn(image.name, tkinter.image_names())
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.BitmapImage)
+
+    def test_image_create_photo(self):
+        self.assertRaises(RuntimeError, tkinter.PhotoImage)
+        root = tkinter.Tk()
+        image = tkinter.PhotoImage()
+        self.assertIn(image.name, tkinter.image_names())
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.PhotoImage)
+
+
 class BitmapImageTest(AbstractTkTest, unittest.TestCase):
 
     @classmethod
@@ -330,7 +371,7 @@ class PhotoImageTest(AbstractTkTest, unittest.TestCase):
         self.assertEqual(image.transparency_get(4, 6), False)
 
 
-tests_gui = (MiscTest, BitmapImageTest, PhotoImageTest,)
+tests_gui = (MiscTest, DefaultRootTest, BitmapImageTest, PhotoImageTest,)
 
 if __name__ == "__main__":
     support.run_unittest(*tests_gui)