delay imports of zmq.ssh.tunnel

until they are actually used.

Prevents unnecessary imports of Paramiko

IPython/kernel/connect.py

@@ -22,7 +22,6 b' from subprocess import Popen, PIPE'
 import tempfile
 
 import zmq
-from zmq.ssh import tunnel
 
 # IPython imports
 from IPython.config import LoggingConfigurable
@@ -342,6 +341,7 b' def tunnel_to_kernel(connection_info, sshserver, sshkey=None):'
     (shell, iopub, stdin, hb) : ints
         The four ports on localhost that have been forwarded to the kernel.
     """
+    from zmq.ssh import tunnel
     if isinstance(connection_info, string_types):
         # it's a path, unpack it
         with open(connection_info) as f:

IPython/parallel/client/client.py

@@ -18,7 +18,6 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
@@ -443,6 +442,7 b' class Client(HasTraits):'
             # default to ssh via localhost
             sshserver = addr
         if self._ssh and password is None:
+            from zmq.ssh import tunnel
             if tunnel.try_passwordless_ssh(sshserver, sshkey, paramiko):
                 password=False
             else:
@@ -467,6 +467,7 b' class Client(HasTraits):'
         self._query_socket = self._context.socket(zmq.DEALER)
 
         if self._ssh:
+            from zmq.ssh import tunnel
             tunnel.tunnel_connection(self._query_socket, cfg['registration'], sshserver, **ssh_kwargs)
         else:
             self._query_socket.connect(cfg['registration'])
@@ -589,6 +590,7 b' class Client(HasTraits):'
 
         def connect_socket(s, url):
             if self._ssh:
+                from zmq.ssh import tunnel
                 return tunnel.tunnel_connection(s, url, sshserver, **ssh_kwargs)
             else:
                 return s.connect(url)

IPython/parallel/engine/engine.py

@@ -14,11 +14,10 b' from getpass import getpass'
 
 import zmq
 from zmq.eventloop import ioloop, zmqstream
-from zmq.ssh import tunnel
 
 from IPython.utils.localinterfaces import localhost
 from IPython.utils.traitlets import (
-    Instance, Dict, Integer, Type, Float, Integer, Unicode, CBytes, Bool
+    Instance, Dict, Integer, Type, Float, Unicode, CBytes, Bool
 )
 from IPython.utils.py3compat import cast_bytes
 
@@ -58,6 +57,11 b' class EngineFactory(RegistrationFactory):'
         help="""The SSH private key file to use when tunneling connections to the Controller.""")
     paramiko=Bool(sys.platform == 'win32', config=True,
         help="""Whether to use paramiko instead of openssh for tunnels.""")
+    
+    @property
+    def tunnel_mod(self):
+        from zmq.ssh import tunnel
+        return tunnel
 
 
     # not configurable:
@@ -97,7 +101,7 b' class EngineFactory(RegistrationFactory):'
             self.sshserver = self.url.split('://')[1].split(':')[0]
 
         if self.using_ssh:
-            if tunnel.try_passwordless_ssh(self.sshserver, self.sshkey, self.paramiko):
+            if self.tunnel_mod.try_passwordless_ssh(self.sshserver, self.sshkey, self.paramiko):
                 password=False
             else:
                 password = getpass("SSH Password for %s: "%self.sshserver)
@@ -108,7 +112,7 b' class EngineFactory(RegistrationFactory):'
             url = disambiguate_url(url, self.location)
             if self.using_ssh:
                 self.log.debug("Tunneling connection to %s via %s", url, self.sshserver)
-                return tunnel.tunnel_connection(s, url, self.sshserver,
+                return self.tunnel_mod.tunnel_connection(s, url, self.sshserver,
                             keyfile=self.sshkey, paramiko=self.paramiko,
                             password=password,
                 )
@@ -120,7 +124,7 b' class EngineFactory(RegistrationFactory):'
             url = disambiguate_url(url, self.location)
             if self.using_ssh:
                 self.log.debug("Tunneling connection to %s via %s", url, self.sshserver)
-                url,tunnelobj = tunnel.open_tunnel(url, self.sshserver,
+                url, tunnelobj = self.tunnel_mod.open_tunnel(url, self.sshserver,
                             keyfile=self.sshkey, paramiko=self.paramiko,
                             password=password,
                 )