require tornado 4.0 for call_later

Author: minrk

ipykernel/iostream.py

@@ -258,9 +258,7 @@ def _schedule_flush(self):
 
         # add_timeout has to be handed to the io thread with add_callback
         def _schedule_in_thread():
-            # 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._flush_timeout = self._io_loop.call_later(self.flush_interval, self._flush)
         self._io_loop.add_callback(_schedule_in_thread)
 
     def flush(self):

setup.py

@@ -83,6 +83,7 @@
     'ipython>=4.0.0',
     'traitlets',
     'jupyter_client',
+    'tornado>=4.0',
 ]
 
 extras_require = setuptools_args['extras_require'] = {