call_later is new in tornado 4

not present in pyzmq's bundled IOLoop

Author: minrk

ipykernel/iostream.py

@@ -1,3 +1,4 @@
+# coding: utf-8
 """Wrappers for forwarding stdout/stderr over zmq"""
 
 # Copyright (c) IPython Development Team.
@@ -245,9 +246,11 @@ def _schedule_flush(self):
             # non-None to avoid races while waiting for _schedule
             self._flush_timeout = 'placeholder'
 
-        # call_later has to be handed to the io thread with add_callback
+        # add_timeout has to be handed to the io thread with add_callback
         def _schedule_in_thread():
-            self._flush_timeout = self._io_loop.call_later(self.flush_interval, self._flush)
+            # FIXME: call_later is a little nicer, if we can require tornado ≥ 4
+            self._flush_timeout = self._io_loop.add_timeout(
+                self._io_loop.time() + self.flush_interval, self._flush)
         self._io_loop.add_callback(_schedule_in_thread)
 
     def flush(self):