stop using deprecated DelayedCallback

in favor of simpler IOLoop.add_timeout

It was added in pyzmq, but deprecated in pyzmq-13.

IPython/html/services/clusters/clustermanager.py

@@ -17,10 +17,9 @@ Authors:
 #-----------------------------------------------------------------------------
 
 from tornado import web
-from zmq.eventloop import ioloop
 
 from IPython.config.configurable import LoggingConfigurable
-from IPython.utils.traitlets import Dict, Instance, CFloat
+from IPython.utils.traitlets import Dict, Instance, Float
 from IPython.core.profileapp import list_profiles_in
 from IPython.core.profiledir import ProfileDir
 from IPython.utils import py3compat
@@ -38,7 +37,7 @@ class ClusterManager(LoggingConfigurable):
 
     profiles = Dict()
 
-    delay = CFloat(1., config=True,
+    delay = Float(1., config=True,
         help="delay (in s) between starting the controller and the engines")
 
     loop = Instance('zmq.eventloop.ioloop.IOLoop')
@@ -133,11 +132,13 @@ class ClusterManager(LoggingConfigurable):
                 esl.stop()
             clean_data()
         cl.on_stop(controller_stopped)
-
-        dc = ioloop.DelayedCallback(lambda: cl.start(), 0, self.loop)
-        dc.start()
-        dc = ioloop.DelayedCallback(lambda: esl.start(n), 1000*self.delay, self.loop)
-        dc.start()
+        loop = self.loop
+        
+        def start():
+            """start the controller, then the engines after a delay"""
+            cl.start()
+            loop.add_timeout(self.loop.time() + self.delay, lambda : esl.start(n))
+        self.loop.add_callback(start)
 
         self.log.debug('Cluster started')
         data['controller_launcher'] = cl