test_sleep() of test_eintr fails on VSTS/macOS.

select.select() sleeps 200 ms, the process is supposed to get a signal every 100 ms, but the test says that the signal handler was not called during the test. All tests pass, the issue seems to be specific to macOS.

Maybe select() cannot be interrupted by SIGALRM on macOS?

https://dev.azure.com/Python/cpython/_build/results?buildId=34604&view=logs

2018-11-26T12:51:16.6867210Z FAIL: test_sleep (__main__.TimeEINTRTest)
2018-11-26T12:51:16.6868140Z ----------------------------------------------------------------------
2018-11-26T12:51:16.6868300Z Traceback (most recent call last):
2018-11-26T12:51:16.6868450Z   File "/Users/vsts/agent/2.142.1/work/1/s/Lib/test/eintrdata/eintr_tester.py", line 73, in tearDown
2018-11-26T12:51:16.6868570Z     self.assertGreater(self.signals, 0)
2018-11-26T12:51:16.6869080Z AssertionError: 0 not greater than 0

2018-11-26T12:49:29.9119300Z os.uname: posix.uname_result(sysname='Darwin', nodename='Mac-329.local', release='17.7.0', version='Darwin Kernel Version 17.7.0: Thu Jun 21 22:53:14 PDT 2018; root:xnu-4570.71.2~1/RELEASE_X86_64', machine='x86_64')


I added the check (which fails) last week, ensure that the signal handler has been called at least once:

* bpo-35189
* commit aac1f81eef971876ba5b1673db9ce6620311c469