It seems like there is a race condition in some tests. Running the same test twice on the idle buildbot worker fails randomly:

130-CURRENT-amd64% ./python -m test test_socket -v -m test.test_socket.RecvmsgSCTPStreamTest.testRecvmsgAfterClose
== CPython 3.9.0a4+ (heads/master:6ff79f6582, Mar 16 2020, 22:07:47) [Clang 10.0.0 (git@github.com:llvm/llvm-project.git llvmorg-10.0.0-rc3-1-gc290c
== FreeBSD-13.0-CURRENT-amd64-64bit-ELF little-endian
== cwd: /usr/home/haypo/python/master/build/test_python_31444
== CPU count: 2
== encodings: locale=UTF-8, FS=utf-8
(...)
testRecvmsgAfterClose (test.test_socket.RecvmsgSCTPStreamTest) ... ok
(...)

130-CURRENT-amd64% ./python -m test test_socket -v -m test.test_socket.RecvmsgSCTPStreamTest.testRecvmsgAfterClose
(...)
testRecvmsgAfterClose (test.test_socket.RecvmsgSCTPStreamTest) ... ERROR

======================================================================
ERROR: testRecvmsgAfterClose (test.test_socket.RecvmsgSCTPStreamTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/home/haypo/python/master/Lib/test/test_socket.py", line 342, in _setUp
    self.__setUp()
  File "/usr/home/haypo/python/master/Lib/test/test_socket.py", line 2533, in setUp
    super().setUp()
  File "/usr/home/haypo/python/master/Lib/test/test_socket.py", line 646, in setUp
    conn, addr = self.serv.accept()
  File "/usr/home/haypo/python/master/Lib/socket.py", line 293, in accept
    fd, addr = self._accept()
ConnectionAbortedError: [Errno 53] Software caused connection abort
(...)