Comment 1 for bug 1387993

The end of the launchpad-buildd log reads:

2014-10-30 14:31:43+0000 [-] cp: failed to extend 'debian/insighttoolkit4-python/usr/lib/ITK-4.6/Python/itkDiscreteGaussianImageFilterPython.py': No space left on device
2014-10-30 14:31:43+0000 [-] Unhandled Error
        Traceback (most recent call last):
          File "/usr/lib/python2.7/dist-packages/twisted/python/log.py", line 88, in callWithLogger
            return callWithContext({"system": lp}, func, *args, **kw)
          File "/usr/lib/python2.7/dist-packages/twisted/python/log.py", line 73, in callWithContext
            return cont2014-10-30 14:31:45+0000 [-] Iterating with success flag 1 against stage SBUILD
2014-10-30 14:31:45+0000 [-] Returning build status: PACKAGEFAIL
2014-10-30 14:31:45+0000 [-] unexpected error in processEnded
        Traceback (most recent call last):
          File "/usr/lib/python2.7/dist-packages/twisted/internet/process.py", line 46, in reapAllProcesses
            process.reapProcess()
          File "/usr/lib/python2.7/dist-packages/twisted/internet/process.py", line 312, in reapProcess
            self.processEnded(status)
          File "/usr/lib/python2.7/dist-packages/twisted/internet/_baseprocess.py", line 48, in processEnded
            self.maybeCallProcessEnded()
          File "/usr/lib/python2.7/dist-packages/twisted/internet/process.py", line 912, in maybeCallProcessEnded
            _BaseProcess.maybeCallProcessEnded(self)
        --- <exception caught here> ---
          File "/usr/lib/python2.7/dist-packages/twisted/internet/_baseprocess.py", line 60, in maybeCallProcessEnded
            proto.processEnded(Failure(reason))
          File "/usr/lib/launchpad-buildd/lpbuildd/slave.py", line 93, in processEnded
            self.notify(statusobject.value.exitCode)
          File "/usr/lib/launchpad-buildd/lpbuildd/debian.py", line 128, in iterate
            func(success)
          File "/usr/lib/launchpad-buildd/lpbuildd/binarypackage.py", line 135, in iterate_SBUILD
            self.doReapProcesses(self._state)
          File "/usr/lib/launchpad-buildd/lpbuildd/slave.py", line 157, in doReapProcesses
            iterate=iterate)
          File "/usr/lib/launchpad-buildd/lpbuildd/slave.py", line 128, in runSubProcess
            self._slave.log("RUN: %s %r\n" % (command, args))
          File "/usr/lib/launchpad-buildd/lpbuildd/slave.py", line 448, in log
            self._log.flush()
        exceptions.IOError: [Errno 28] No space left on device

We probably need to ensure that we cope with ENOSPC on the log, at least when we've already decided to fail the build anyway.