bpo-37148: Fix asyncio test that check for warning when running the test suite with huntleaks

[pablogsal]

https://bugs.python.org/issue37148

[pablogsal]

Tested locally:

❯ ./python.exe -m test test_asyncio -m test_stream_writer_create_warning -R :
Run tests sequentially
0:00:00 load avg: 1.96 [1/1] test_asyncio
beginning 9 repetitions
123456789
.........

== Tests result: SUCCESS ==

1 test OK.

Total duration: 1 sec 975 ms
Tests result: SUCCESS

without the patch:

❯ ./python.exe -m test test_asyncio -m test_stream_writer_create_warning -R :
Run tests sequentially
0:00:00 load avg: 2.21 [1/1] test_asyncio
beginning 9 repetitions
123456789
.test test_asyncio failed -- Traceback (most recent call last):
  File "/Users/pgalindo3/github/cpython/Lib/test/test_asyncio/test_streams.py", line 1238, in test_stream_writer_create_warning
    asyncio.StreamWriter
AssertionError: DeprecationWarning not triggered

test_asyncio failed

== Tests result: FAILURE ==

1 test failed:
    test_asyncio

Total duration: 581 ms
Tests result: FAILURE

[asvetlov]

@pablogsal there is another PR for improving streams tests stability: #13790
I'd like to merge it but waiting for review

[pablogsal]

Thanks, @asvetlov, I will try to review it as soon as I merge this and unblock the refleaks buildbots to allow beta1 release (they are still red as of now).

[ambv]

@pablogsal: https://buildbot.python.org/all/#/builders/168/builds/1150

[vstinner]

@pablogsal: https://buildbot.python.org/all/#/builders/168/builds/1150

This failure is unrelated to this fix. It will be fixed by #13790 which has just been merged ;-) (but not part of this build)

[tirkarthi]

There is a test__xxsubinterpreters in the build for #13790 : https://buildbot.python.org/all/#/builders/168/builds/1151/steps/5/logs/stdio

======================================================================
FAIL: test_still_running (test.test__xxsubinterpreters.DestroyTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/test__xxsubinterpreters.py", line 765, in test_still_running
    interpreters.destroy(interp)
AssertionError: RuntimeError not raised
----------------------------------------------------------------------
Ran 112 tests in 30.951s
FAILED (failures=1, skipped=5)
test test__xxsubinterpreters failed

Edit : Probably unrelated to the asyncio changes in the buildbot run but thought to add it here

[vstinner]

@tirkarthi: Please open a new issue on bugs.python.org, this issue is unrelated.