bpo-37309: First idlelib/NEWS.txt for 3.9.0

[terryjreedy]

https://bugs.python.org/issue37309

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 FreeBSD Shared 3.8 has failed when building commit 6d6418a.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/374/builds/10) and take a look at the build logs.
4. Check if the failure is related to this commit (6d6418a) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/374/builds/10

Failed tests:

• test_asyncio

Failed subtests:

• test_communicate - test.test_asyncio.test_subprocess.SubprocessMultiLoopWatcherTests

Summary of the results of the build (if available):

== Tests result: FAILURE then FAILURE ==

402 tests OK.

10 slowest tests:

• test_tokenize: 6 min 54 sec
• test_tools: 6 min 7 sec
• test_multiprocessing_spawn: 6 min
• test_lib2to3: 4 min 49 sec
• test_concurrent_futures: 4 min 27 sec
• test_multiprocessing_forkserver: 3 min 58 sec
• test_asyncio: 3 min 28 sec
• test_multiprocessing_fork: 3 min 24 sec
• test_pickle: 2 min 35 sec
• test_subprocess: 2 min 32 sec

1 test failed:
test_asyncio

20 tests skipped:
test_dbm_gnu test_devpoll test_epoll test_gdb test_idle test_ioctl
test_msilib test_ossaudiodev test_spwd test_startfile test_tcl
test_tix test_tk test_ttk_guionly test_ttk_textonly test_turtle
test_winconsoleio test_winreg test_winsound test_zipfile64

1 re-run test:
test_asyncio

Total duration: 26 min 42 sec

Click to see traceback logs

Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.8.koobs-freebsd-564d/build/Lib/test/test_asyncio/test_tasks.py", line 3210, in test_run_coroutine_threadsafe_with_timeout
    self.loop.run_until_complete(future)
AssertionError: TimeoutError not raised


Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.8.koobs-freebsd-564d/build/Lib/test/test_asyncio/test_subprocess.py", line 147, in test_communicate
    exitcode, stdout = self.loop.run_until_complete(task)
  File "/usr/home/buildbot/python/3.8.koobs-freebsd-564d/build/Lib/asyncio/base_events.py", line 608, in run_until_complete
    return future.result()
  File "/usr/home/buildbot/python/3.8.koobs-freebsd-564d/build/Lib/asyncio/tasks.py", line 490, in wait_for
    raise exceptions.TimeoutError()
asyncio.exceptions.TimeoutError