Lots of failures the last three days on multiple builds:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/buildbot/process/buildstep.py", line 545, in _startStep_2
    doStep.addCallback(self._startStep_3)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 298, in addCallback
    callbackKeywords=kw)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 287, in addCallbacks
    self._runCallbacks()
  File "/usr/lib/python2.7/dist-packages/twisted/internet/defer.py", line 545, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
--- <exception caught here> ---
  File "/usr/lib/python2.7/dist-packages/buildbot/process/buildstep.py", line 551, in _startStep_3
    if self.start() == SKIPPED:
  File "/usr/lib/python2.7/dist-packages/buildbot/steps/master.py", line 112, in start
    path=self.path, usePTY=self.usePTY, env=env )
  File "/usr/lib/python2.7/dist-packages/twisted/internet/posixbase.py", line 337, in spawnProcess
    processProtocol, uid, gid, childFDs)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/process.py", line 683, in __init__
    self._fork(path, uid, gid, executable, args, environment, fdmap=fdmap)
  File "/usr/lib/python2.7/dist-packages/twisted/internet/process.py", line 390, in _fork
    self.pid = os.fork()
exceptions.OSError: [Errno 12] Cannot allocate memory