[3.6] bpo-31234: Add test.support.wait_threads_exit() (GH-3578) (GH-7315)

* bpo-31234: Add test.support.wait_threads_exit() (GH-3578)

Use _thread.count() to wait until threads exit. The new context
manager prevents the "dangling thread" warning.

(cherry picked from commit ff40ecda73178dfcad24e26240d684356ef20793)

* bpo-31234: Try to fix lock_tests warning (#3557)

Try to fix the "Warning -- threading_cleanup() failed to cleanup 1
threads" warning in test.lock_tests: wait a little bit longer to give
time to the threads to complete.

Warning seen on test_thread and test_importlib.

(cherry picked from commit 096ae3373abac2c8b3a26a3fe33cc8bd4cbccd4e)

1 files changed, 8 insertions, 6 deletions

diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index b42314f..43ef22b 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -125,9 +125,10 @@ class ThreadTests(BaseTestCase):
             done.set()
         done = threading.Event()
         ident = []
-        _thread.start_new_thread(f, ())
-        done.wait()
-        self.assertIsNotNone(ident[0])
+        with support.wait_threads_exit():
+            tid = _thread.start_new_thread(f, ())
+            done.wait()
+            self.assertEqual(ident[0], tid)
         # Kill the "immortal" _DummyThread
         del threading._active[ident[0]]
 
@@ -165,9 +166,10 @@ class ThreadTests(BaseTestCase):
 
         mutex = threading.Lock()
         mutex.acquire()
-        tid = _thread.start_new_thread(f, (mutex,))
-        # Wait for the thread to finish.
-        mutex.acquire()
+        with support.wait_threads_exit():
+            tid = _thread.start_new_thread(f, (mutex,))
+            # Wait for the thread to finish.
+            mutex.acquire()
         self.assertIn(tid, threading._active)
         self.assertIsInstance(threading._active[tid], threading._DummyThread)
         #Issue 29376