gh-76785: Update test.support.interpreters to Align With PEP 734 (gh-115566)

This brings the code under test.support.interpreters, and the corresponding extension modules, in line with recent updates to PEP 734.

(Note: PEP 734 has not been accepted at this time.  However, we are using an internal copy of the implementation in the test suite to exercise the existing subinterpreters feature.)

Lib/test/test_interpreters/utils.py

@@ -4,8 +4,9 @@ import os.path
 import subprocess
 import sys
 import tempfile
-import threading
 from textwrap import dedent
+import threading
+import types
 import unittest
 
 from test import support
@@ -41,7 +42,7 @@ def _run_output(interp, request, init=None):
     with rpipe:
         if init:
             interp.prepare_main(init)
-        interp.exec_sync(script)
+        interp.exec(script)
         return rpipe.read()
 
 
@@ -49,7 +50,7 @@ def _run_output(interp, request, init=None):
 def _running(interp):
     r, w = os.pipe()
     def run():
-        interp.exec_sync(dedent(f"""
+        interp.exec(dedent(f"""
             # wait for "signal"
             with open({r}) as rpipe:
                 rpipe.read()
@@ -84,6 +85,18 @@ class TestBase(unittest.TestCase):
         self.addCleanup(lambda: os_helper.rmtree(tempdir))
         return tempdir
 
+    @contextlib.contextmanager
+    def captured_thread_exception(self):
+        ctx = types.SimpleNamespace(caught=None)
+        def excepthook(args):
+            ctx.caught = args
+        orig_excepthook = threading.excepthook
+        threading.excepthook = excepthook
+        try:
+            yield ctx
+        finally:
+            threading.excepthook = orig_excepthook
+
     def make_script(self, filename, dirname=None, text=None):
         if text:
             text = dedent(text)