EpollPoller registers with mask EPOLLIN, but filters as if also expecting EPOLLHUP

[moreati]

EpollPoller registers with the mask EPOLLIN | EPOLLOUT

mitogen/mitogen/parent.py

Lines 1044 to 1047 in bb9c51b

	def _control(self, fd):
	mitogen.core._vv and IOLOG.debug('%r._control(%r)', self, fd)
	mask = (((fd in self._rfds) and select.EPOLLIN) |
	((fd in self._wfds) and select.EPOLLOUT))

but when looping over a poll result it filters read file descriptors (self._rfds) on EPOLLIN | EPOLLHUP

mitogen/mitogen/parent.py

Lines 1080 to 1081 in bb9c51b

	_inmask = (getattr(select, 'EPOLLIN', 0) |
	getattr(select, 'EPOLLHUP', 0))

mitogen/mitogen/parent.py

Lines 1089 to 1090 in bb9c51b

	for fd, event in events:
	if event & self._inmask:

I'm not familiar with epoll() so this may be working as intended, but it feels like a bug. Noticed while investigating #957.