[Twisted-Python] Weird PyPY twisted.internet.defer.TimeoutError ERROR*12 during full test run

[Daniel Sutcliffe]

During the PyPy2.7 5.8.0 testsuite run (actually happens under PyPy3.5
5.8.0 too) there always seems to be a group of 12 ERROR due to:
  twisted.internet.defer.TimeoutError

For the buildbot: https://buildbot.twistedmatrix.com/builders/ubuntu16.04-pypy5/
they seem to pretty much consistently happen during:
  twisted.protocols.test.test_tls.TLSMemoryBIOTests.test_hugeWrite_TLSv1_1
but running in my own environment(s) I also always see the 12
TimoutError but they can occur in a variety of different tests, I've
seen them in these as well as the above:
   twisted.news.test.test_news.NewsTests.testArticleRequest
   twisted.names.test.test_server.DNSServerFactoryTests.test_verboseDefault
   twisted.positioning.test.test_nmea.BrokenSentenceCallbackTests.test_dontSwallowCallbackException
and a bunch of others.

Always exactly 12 and always during same test for a single test run.
I've not been able to reproduce running anything but the full
testsuite - but they have always occured for me during full run.

Just wondered if anybody with more experience had a clue/idea as to
why this could happen (why 12), and how I could go about tracking down
the root cause.

Getting close to having PyPy be able to run twisted tests with no
FAILs but I have no idea what might be causing this.
Cheers
/dan
-- 
Daniel Sutcliffe <dansut at gmail.com>