• Detect and raise an error for several important types of
  programming errors even if Python interpreter optimizations are
  enabled with -O or PYTHONOPTIMIZE. Previously these would go
  undetected if optimizations were enabled, potentially leading to
  erratic, difficult to debug behaviour.
• Fix an AttributeError from gevent.queue.Queue when peek
  was called on an empty Queue. Reported in #643 by michaelvol.
• Make SIGCHLD handlers specified to signal.signal work with
  the child watchers that are used by default. Also make
  os.waitpid work with a first argument of -1. Noted by users of gunicorn.
• Under Python 2, any timeout set on a socket would be ignored when
  using the results of socket.makefile. Reported in #644
  by Karan Lyons.