the same tree built on Windows OK
A typical error is
2021-12-17T05:02:10.2803270Z File "/Users/runner/work/1/s/.tox/alldeps-withcov-posix/lib/python3.7/site-packages/twisted/internet/test/test_unix.py", line 54, in <module>
2021-12-17T05:02:10.2803990Z from twisted.internet.test.test_tcp import (
2021-12-17T05:02:10.2805100Z File "/Users/runner/work/1/s/.tox/alldeps-withcov-posix/lib/python3.7/site-packages/twisted/internet/test/test_tcp.py", line 128, in <module>
2021-12-17T05:02:10.2806030Z from twisted.internet.test import _posixifaces
2021-12-17T05:02:10.2807270Z File "/Users/runner/work/1/s/.tox/alldeps-withcov-posix/lib/python3.7/site-packages/twisted/internet/test/_posixifaces.py", line 31, in <module>
2021-12-17T05:02:10.2807970Z libc = CDLL(find_library("c") or "")
2021-12-17T05:02:10.2808580Z File "/Users/runner/hostedtoolcache/Python/3.7.12/x64/lib/python3.7/ctypes/__init__.py", line 364, in __init__
2021-12-17T05:02:10.2809180Z self._handle = _dlopen(self._name, mode)
2021-12-17T05:02:10.2809720Z builtins.OSError: dlopen(, 6): no suitable image found. Did find:
2021-12-17T05:02:10.2810240Z /usr/local/lib/: not a file
2021-12-17T05:02:10.2810650Z /usr/local/lib: not a file
2021-12-17T05:02:10.2811050Z /usr/lib/: not a file
2021-12-17T05:02:10.2811440Z /usr/lib: not a file
2021-12-17T05:02:10.2811670Z
2021-12-17T05:02:10.2812020Z twisted.internet.test.test_unix
should this test be running on Mac at all?