remove IPython.external.ssh

This code moved to zmq a while ago, let’s just depend on that.

IPython/kernel/connect.py

@@ -22,9 +22,7 b' from subprocess import Popen, PIPE'
 import tempfile
 
 import zmq
-
-# external imports
-from IPython.external.ssh import tunnel
+from zmq.ssh import tunnel
 
 # IPython imports
 from IPython.config import LoggingConfigurable

IPython/parallel/client/client.py

@@ -18,6 +18,7 b' from pprint import pprint'
 pjoin = os.path.join
 
 import zmq
+from zmq.ssh import tunnel
 
 from IPython.config.configurable import MultipleInstanceError
 from IPython.core.application import BaseIPythonApplication
@@ -32,7 +33,6 b' from IPython.utils.py3compat import cast_bytes, string_types, xrange, iteritems'
 from IPython.utils.traitlets import (HasTraits, Integer, Instance, Unicode,
                                     Dict, List, Bool, Set, Any)
 from IPython.external.decorator import decorator
-from IPython.external.ssh import tunnel
 
 from IPython.parallel import Reference
 from IPython.parallel import error

IPython/parallel/engine/engine.py

@@ -14,9 +14,8 b' from getpass import getpass'
 
 import zmq
 from zmq.eventloop import ioloop, zmqstream
+from zmq.ssh import tunnel
 
-from IPython.external.ssh import tunnel
-# internal
 from IPython.utils.localinterfaces import localhost
 from IPython.utils.traitlets import (
     Instance, Dict, Integer, Type, Float, Integer, Unicode, CBytes, Bool