pythonGH-122864: Fix a unit test which was failing when the test module was

run directly via: `python -m test.test_funcattrs`.

Author: mbyrnepr2

Lib/test/test_funcattrs.py

@@ -98,7 +98,23 @@ def test___globals__(self):
                              (AttributeError, TypeError))
 
     def test___builtins__(self):
-        self.assertIs(self.b.__builtins__, __builtins__)
+        if __name__ == "__main__":
+            # `func.__builtins__` is `builtins.__dict__`.
+            # See:https://bugs.python.org/issue42990
+
+            # When this test is run by executing the current module,
+            # `__builtins__` is the built-in module `builtins`.
+
+            # When this test is run from another module, `__builtins__` is
+            # `builtins.__dict__`
+            # See: https://docs.python.org/3/reference/executionmodel.html#builtins-and-restricted-execution
+
+            import builtins
+            builtins_dict = builtins.__dict__
+        else:
+            builtins_dict = __builtins__
+
+        self.assertIs(self.b.__builtins__, builtins_dict)
         self.cannot_set_attr(self.b, '__builtins__', 2,
                              (AttributeError, TypeError))
 
@@ -108,7 +124,7 @@ def func(s): return len(s)
         ns = {}
         func2 = type(func)(func.__code__, ns)
         self.assertIs(func2.__globals__, ns)
-        self.assertIs(func2.__builtins__, __builtins__)
+        self.assertIs(func2.__builtins__, builtins_dict)
 
         # Make sure that the function actually works.
         self.assertEqual(func2("abc"), 3)