Fix the test failures.

Lib/test/test_embed.py

@@ -93,6 +93,8 @@ def setUp(self):
     def tearDown(self):
         os.chdir(self.oldcwd)
 
+    ANY_FAILURE = object()
+
     def run_embedded_interpreter(self, *args, env=None,
                                  timeout=None, returncode=0, input=None,
                                  cwd=None):
@@ -117,7 +119,7 @@ def run_embedded_interpreter(self, *args, env=None,
             p.terminate()
             p.wait()
             raise
-        if returncode is None:
+        if returncode is self.ANY_FAILURE:
             returncode = 1 if p.returncode == 0 else p.returncode
         if p.returncode != returncode and support.verbose:
             print(f"--- {cmd} failed ---")
@@ -234,23 +236,24 @@ def test_replace_main_tstate(self):
                 self.run_embedded_interpreter(
                     'test_replace_main_tstate',
                     # At the moment, this fails because main_tstate gets broken.
-                    returncode=None,
+                    returncode=self.ANY_FAILURE,
                 )
             with self.subTest(reuse=reuse, exec=True):
-                out, _ = self.run_embedded_interpreter(
+                out, rc = self.run_embedded_interpreter(
                     'test_replace_main_tstate',
                     'print("spam!")',
-                    # At the moment, this actually succeeds on all platforms.
-                    returncode=0,
+                    # At the moment, this fails because main_tstate gets broken.
+                    returncode=self.ANY_FAILURE,
                 )
-                self.assertEqual(out.strip(), 'spam!')
+                if rc == 0:
+                    self.assertEqual(out.strip(), 'spam!')
 
     def test_fini_in_subthread(self):
         self.run_embedded_interpreter(
             'test_fini_in_subthread',
             # At the moment, this actually succeeds on all platforms,
             # except for Windows (STATUS_ACCESS_VIOLATION).
-            returncode=None if MS_WINDOWS else 0,
+            returncode=self.ANY_FAILURE if MS_WINDOWS else 0,
         )
 
     def test_fini_in_main_thread_with_other_tstate(self):