[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 3d569fd6dccf9f582bafaca04d3535094cae393e)

1 files changed, 12 insertions, 2 deletions

diff --git a/Lib/tkinter/test/test_tkinter/test_widgets.py b/Lib/tkinter/test/test_tkinter/test_widgets.py
index 4b9b6eb..54eddbf 100644
--- a/Lib/tkinter/test/test_tkinter/test_widgets.py
+++ b/Lib/tkinter/test/test_tkinter/test_widgets.py
@@ -5,7 +5,8 @@ import os
 from test.support import requires
 
 from tkinter.test.support import (tcl_version, requires_tcl,
-                                  get_tk_patchlevel, widget_eq)
+                                  get_tk_patchlevel, widget_eq,
+                                  AbstractDefaultRootTest)
 from tkinter.test.widget_tests import (
     add_standard_options, noconv, pixels_round,
     AbstractWidgetTest, StandardOptionsTests, IntegerSizeTests, PixelSizeTests,
@@ -1295,12 +1296,21 @@ class MessageTest(AbstractWidgetTest, unittest.TestCase):
         self.checkIntegerParam(widget, 'aspect', 250, 0, -300)
 
 
+class DefaultRootTest(AbstractDefaultRootTest, unittest.TestCase):
+
+    def test_frame(self):
+        self._test_widget(tkinter.Frame)
+
+    def test_label(self):
+        self._test_widget(tkinter.Label)
+
+
 tests_gui = (
         ButtonTest, CanvasTest, CheckbuttonTest, EntryTest,
         FrameTest, LabelFrameTest,LabelTest, ListboxTest,
         MenubuttonTest, MenuTest, MessageTest, OptionMenuTest,
         PanedWindowTest, RadiobuttonTest, ScaleTest, ScrollbarTest,
-        SpinboxTest, TextTest, ToplevelTest,
+        SpinboxTest, TextTest, ToplevelTest, DefaultRootTest,
 )
 
 if __name__ == '__main__':