IPython.parallel logging cleanup

* prevent log propagation (fixes duplicate messages on ipcluster exit)
* hook up util.signal_children log message to running application

IPython/parallel/apps/baseapp.py

@@ -162,6 +162,10 b' class BaseParallelApplication(BaseIPythonApplication):'
             self._log_formatter = logging.Formatter("[%(name)s] %(message)s")
             self._log_handler.setFormatter(self._log_formatter)
             self.log.addHandler(self._log_handler)
+        # do not propagate log messages to root logger
+        # ipcluster app will sometimes print duplicate messages during shutdown
+        # if this is 1 (default):
+        self.log.propagate = False
 
     def write_pid_file(self, overwrite=False):
         """Create a .pid file in the pid_dir with my pid.

IPython/parallel/util.py

@@ -40,6 +40,7 b' import zmq'
 from zmq.log import handlers
 
 # IPython imports
+from IPython.config.application import Application
 from IPython.utils.pickleutil import can, uncan, canSequence, uncanSequence
 from IPython.utils.newserialized import serialize, unserialize
 from IPython.zmq.log import EnginePUBHandler
@@ -391,7 +392,8 b' def select_random_ports(n):'
 def signal_children(children):
     """Relay interupt/term signals to children, for more solid process cleanup."""
     def terminate_children(sig, frame):
-        logging.critical("Got signal %i, terminating children..."%sig)
+        log = Application.instance().log
+        log.critical("Got signal %i, terminating children..."%sig)
         for child in children:
             child.terminate()