bpo-44904: Fix classmethod property bug in doctest module (GH-28838)


The doctest module raised an error if a docstring contained an example that
attempted to access a classmethod property. (Stacking '@classmethod' on top of
`@property` has been supported since Python 3.9; see
https://docs.python.org/3/howto/descriptor.htmlGH-class-methods.)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
(cherry picked from commit b1302abcc8a4be5f39b4d60a1ce28032b77655b3)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index 7f8ccd3..9703f87 100644
--- a/Lib/test/test_doctest.py
+++ b/Lib/test/test_doctest.py
@@ -96,6 +96,17 @@ def a_classmethod(cls, v):
         22
         """)
 
+    a_class_attribute = 42
+
+    @classmethod
+    @property
+    def a_classmethod_property(cls):
+        """
+        >>> print(SampleClass.a_classmethod_property)
+        42
+        """
+        return cls.a_class_attribute
+
     class NestedClass:
         """
         >>> x = SampleClass.NestedClass(5)
@@ -501,6 +512,7 @@ def basics(): r"""
      1  SampleClass.NestedClass.__init__
      1  SampleClass.__init__
      2  SampleClass.a_classmethod
+     1  SampleClass.a_classmethod_property
      1  SampleClass.a_property
      1  SampleClass.a_staticmethod
      1  SampleClass.double
@@ -556,6 +568,7 @@ def basics(): r"""
      1  some_module.SampleClass.NestedClass.__init__
      1  some_module.SampleClass.__init__
      2  some_module.SampleClass.a_classmethod
+     1  some_module.SampleClass.a_classmethod_property
      1  some_module.SampleClass.a_property
      1  some_module.SampleClass.a_staticmethod
      1  some_module.SampleClass.double
@@ -597,6 +610,7 @@ def basics(): r"""
      1  SampleClass.NestedClass.__init__
      1  SampleClass.__init__
      2  SampleClass.a_classmethod
+     1  SampleClass.a_classmethod_property
      1  SampleClass.a_property
      1  SampleClass.a_staticmethod
      1  SampleClass.double
@@ -617,6 +631,7 @@ def basics(): r"""
      0  SampleClass.NestedClass.square
      1  SampleClass.__init__
      2  SampleClass.a_classmethod
+     1  SampleClass.a_classmethod_property
      1  SampleClass.a_property
      1  SampleClass.a_staticmethod
      1  SampleClass.double