[users at bb.net] Logging to unix domain sockets confuses npm

[Dan Kegel]

Hi folks.  I just discovered why some of my bots are hanging on npm projects:
npm itself is using a module which calls the unix utility 'resize -u',
which seems to hang on mac osx 10.11 in an ioctl on osx if stderr is a
unix domain socket.

https://github.com/yeoman/update-notifier/issues/125
https://github.com/sindresorhus/term-size/issues/3

Not buildbot's fault, but maybe this could be of interest to a few
buildbot users.