gh-127949: deprecate `asyncio.set_event_loop_policy` (#128024)

First step towards deprecating the asyncio policy system.
This deprecates `asyncio.set_event_loop_policy` and will be removed in Python 3.16. 

1 files changed, 13 insertions, 9 deletions

diff --git a/Lib/test/test_asyncio/test_events.py b/Lib/test/test_asyncio/test_events.py
index 2ab638dc527..50df1b6ff9e 100644
--- a/Lib/test/test_asyncio/test_events.py
+++ b/Lib/test/test_asyncio/test_events.py
@@ -36,10 +36,10 @@ from test import support
 from test.support import socket_helper
 from test.support import threading_helper
 from test.support import ALWAYS_EQ, LARGEST, SMALLEST
-
+from test.support import warnings_helper
 
 def tearDownModule():
-    asyncio.set_event_loop_policy(None)
+    asyncio._set_event_loop_policy(None)
 
 
 def broken_unix_getsockname():
@@ -2764,13 +2764,17 @@ class PolicyTests(unittest.TestCase):
         self.assertIs(policy, asyncio.get_event_loop_policy())
 
     def test_set_event_loop_policy(self):
-        self.assertRaises(
-            TypeError, asyncio.set_event_loop_policy, object())
+        with self.assertWarnsRegex(
+                DeprecationWarning, "'set_event_loop_policy' is deprecated"):
+            self.assertRaises(
+                TypeError, asyncio.set_event_loop_policy, object())
 
         old_policy = asyncio.get_event_loop_policy()
 
         policy = asyncio.DefaultEventLoopPolicy()
-        asyncio.set_event_loop_policy(policy)
+        with self.assertWarnsRegex(
+                DeprecationWarning, "'set_event_loop_policy' is deprecated"):
+            asyncio.set_event_loop_policy(policy)
         self.assertIs(policy, asyncio.get_event_loop_policy())
         self.assertIsNot(policy, old_policy)
 
@@ -2857,7 +2861,7 @@ class GetEventLoopTestsMixin:
 
         old_policy = asyncio.get_event_loop_policy()
         try:
-            asyncio.set_event_loop_policy(Policy())
+            asyncio._set_event_loop_policy(Policy())
             loop = asyncio.new_event_loop()
 
             with self.assertRaises(TestError):
@@ -2885,7 +2889,7 @@ class GetEventLoopTestsMixin:
                 asyncio.get_event_loop()
 
         finally:
-            asyncio.set_event_loop_policy(old_policy)
+            asyncio._set_event_loop_policy(old_policy)
             if loop is not None:
                 loop.close()
 
@@ -2897,7 +2901,7 @@ class GetEventLoopTestsMixin:
     def test_get_event_loop_returns_running_loop2(self):
         old_policy = asyncio.get_event_loop_policy()
         try:
-            asyncio.set_event_loop_policy(asyncio.DefaultEventLoopPolicy())
+            asyncio._set_event_loop_policy(asyncio.DefaultEventLoopPolicy())
             loop = asyncio.new_event_loop()
             self.addCleanup(loop.close)
 
@@ -2923,7 +2927,7 @@ class GetEventLoopTestsMixin:
                 asyncio.get_event_loop()
 
         finally:
-            asyncio.set_event_loop_policy(old_policy)
+            asyncio._set_event_loop_policy(old_policy)
             if loop is not None:
                 loop.close()