tests fail when using pure-python instead of _asyncio

[mattip]

BPO	45011
Nosy	@asvetlov, @ambv, @serhiy-storchaka, @mattip, @1st1, @pablogsal, @miss-islington
PRs	bpo-45011: Fix test_asyncio without C module _asyncio #27968 [3.10] bpo-45011: Fix test_asyncio without C module _asyncio (GH-27968) #27969 [3.9] bpo-45011: Fix test_asyncio without C module _asyncio (GH-27968) #27970

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-08-26.18:06:38.989>
created_at = <Date 2021-08-26.08:34:05.218>
labels = ['type-bug', '3.9', '3.10', '3.11', 'release-blocker', 'expert-asyncio']
title = 'tests fail when using pure-python instead of _asyncio'
updated_at = <Date 2021-08-26.18:06:38.988>
user = 'https://github.com/mattip'

bugs.python.org fields:

activity = <Date 2021-08-26.18:06:38.988>
actor = 'lukasz.langa'
assignee = 'none'
closed = True
closed_date = <Date 2021-08-26.18:06:38.989>
closer = 'lukasz.langa'
components = ['asyncio']
creation = <Date 2021-08-26.08:34:05.218>
creator = 'mattip'
dependencies = []
files = []
hgrepos = []
issue_num = 45011
keywords = ['patch']
message_count = 5.0
messages = ['400322', '400333', '400343', '400345', '400361']
nosy_count = 7.0
nosy_names = ['asvetlov', 'lukasz.langa', 'serhiy.storchaka', 'mattip', 'yselivanov', 'pablogsal', 'miss-islington']
pr_nums = ['27968', '27969', '27970']
priority = 'release blocker'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45011'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[mattip]

PyPy has no asyncio c-extension module _asyncio. I see stdlib test failures when running the tests in test/test_asyncio/*.py. If I disable _asyncio in Lib/asyncio/events.py (at the end of the file) I see similar failures in CPython3.8 on Ubuntu 20.04 in

test_buffered_proto.py test_buffered_proto_create_connection

test_sslproto.py test_create_connection_memory_leak, test_handshake_timeout, test_start_tls_client_buf_proto_1,

Also this test depends on _CFuture
test_futures.py

[serhiy-storchaka]

I do not know why asyncio.events._get_running_loop was patched in FunctionalTestCaseMixin.