Pablo wrote on the buildbot-status mailing list:
"It seems that this worker has some bad upgrade to SSL as all branches fail at the same time:"

AMD64 Debian root 3.7:
https://buildbot.python.org/all/#builders/3/builds/8

======================================================================
ERROR: test_sock_sendfile_exception (test.test_asyncio.test_unix_events.SelectorEventLoopUnixSockSendfileTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 613, in test_sock_sendfile_exception
    sock, proto = self.prepare()
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 491, in prepare
    self.run_loop(self.loop.sock_connect(sock, (support.HOST, port)))
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 481, in run_loop
    return self.loop.run_until_complete(coro)
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/asyncio/base_events.py", line 579, in run_until_complete
    return future.result()
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/asyncio/selector_events.py", line 460, in sock_connect
    if isinstance(sock, ssl.SSLSocket):
AttributeError: 'NoneType' object has no attribute 'SSLSocket'
======================================================================
ERROR: test_sock_sendfile_iobuffer (test.test_asyncio.test_unix_events.SelectorEventLoopUnixSockSendfileTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 524, in test_sock_sendfile_iobuffer
    sock, proto = self.prepare()
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 491, in prepare
    self.run_loop(self.loop.sock_connect(sock, (support.HOST, port)))
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 481, in run_loop
    return self.loop.run_until_complete(coro)
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/asyncio/base_events.py", line 579, in run_until_complete
    return future.result()
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/asyncio/selector_events.py", line 460, in sock_connect
    if isinstance(sock, ssl.SSLSocket):
AttributeError: 'NoneType' object has no attribute 'SSLSocket'
======================================================================
ERROR: test_sock_sendfile_not_a_file (test.test_asyncio.test_unix_events.SelectorEventLoopUnixSockSendfileTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 515, in test_sock_sendfile_not_a_file
    sock, proto = self.prepare()
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 491, in prepare
    self.run_loop(self.loop.sock_connect(sock, (support.HOST, port)))
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/test/test_asyncio/test_unix_events.py", line 481, in run_loop
    return self.loop.run_until_complete(coro)
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/asyncio/base_events.py", line 579, in run_until_complete
    return future.result()
  File "/root/buildarea/3.7.angelico-debian-amd64/build/Lib/asyncio/selector_events.py", line 460, in sock_connect
    if isinstance(sock, ssl.SSLSocket):
AttributeError: 'NoneType' object has no attribute 'SSLSocket'

"""
Python build finished successfully!
The necessary bits to build these optional modules were not found:
_ssl                  _tkinter              _uuid              
"""

The _ssl module was not built on this worker, so why test_ssl was not skipped?

I don't see test_ssl.py in the logs. test_unix_events.py is failing because it is missing a check for _ssl.

Same issue on AMD64 Debian root 3.8:
https://buildbot.python.org/all/#builders/162/builds/14

And AMD64 Debian root 3.x:
https://buildbot.python.org/all/#builders/225/builds/28

Sorry, my fault.

The problem was introduced by https://bugs.python.org/issue37404. I created https://github.com/python/cpython/pull/17526 to fix the problem and address a minor performance regression.

New changeset 82b4950b5e92bec343a436b3f9c116400b66e1b9 by Victor Stinner in branch 'master':
bpo-39006: Fix asyncio when the ssl module is missing (GH-17524)
https://github.com/python/cpython/commit/82b4950b5e92bec343a436b3f9c116400b66e1b9

I wrote a fix which was approved by Andrew Svetlov. Andrew prefers my PR than Christian's PR 17526, so I merged my PR instead. See PR 17526 discussion for the rationale.

I merged your PR to master, 3.7 and 3.8 backport will automatically follow. I close the issue.

New changeset b22183f2738e0e6c23f8c5fb5b232768c184ec96 by Miss Islington (bot) in branch '3.8':
bpo-39006: Fix asyncio when the ssl module is missing (GH-17524)
https://github.com/python/cpython/commit/b22183f2738e0e6c23f8c5fb5b232768c184ec96

New changeset a0078d9a3335a5e99afe97590fdcb8e2f526ed7b by Miss Islington (bot) in branch '3.7':
bpo-39006: Fix asyncio when the ssl module is missing (GH-17524)
https://github.com/python/cpython/commit/a0078d9a3335a5e99afe97590fdcb8e2f526ed7b