Fix import of socketserver on Python 3.

Closes gh-5382

IPython/external/ssh/forward.py

@@ -1,88 +1,91 b''
 #
 # This file is adapted from a paramiko demo, and thus licensed under LGPL 2.1.
 # Original Copyright (C) 2003-2007  Robey Pointer <[e-mail]>
 # Edits Copyright (C) 2010 The IPython Team
 #
 # Paramiko is free software; you can redistribute it and/or modify it under the
 # terms of the GNU Lesser General Public License as published by the Free
 # Software Foundation; either version 2.1 of the License, or (at your option)
 # any later version.
 #
 # Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
 # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 # A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
 # details.
 #
 # You should have received a copy of the GNU Lesser General Public License
 # along with Paramiko; if not, write to the Free Software Foundation, Inc.,
 # 51 Franklin Street, Fifth Floor, Boston, MA  02111-1301  USA.
 
 """
 Sample script showing how to do local port forwarding over paramiko.
 
 This script connects to the requested SSH server and sets up local port
 forwarding (the openssh -L option) from a local port through a tunneled
 connection to a destination reachable from the SSH server machine.
 """
 
 from __future__ import print_function
 
 import logging
 import select
-import SocketServer
+try:  # Python 3
+    import socketserver
+except ImportError:  # Python 2
+    import SocketServer as socketserver
 
 logger = logging.getLogger('ssh')
 
-class ForwardServer (SocketServer.ThreadingTCPServer):
+class ForwardServer (socketserver.ThreadingTCPServer):
     daemon_threads = True
     allow_reuse_address = True
     
 
-class Handler (SocketServer.BaseRequestHandler):
+class Handler (socketserver.BaseRequestHandler):
 
     def handle(self):
         try:
             chan = self.ssh_transport.open_channel('direct-tcpip',
                                                    (self.chain_host, self.chain_port),
                                                    self.request.getpeername())
         except Exception as e:
             logger.debug('Incoming request to %s:%d failed: %s' % (self.chain_host,
                                                               self.chain_port,
                                                               repr(e)))
             return
         if chan is None:
             logger.debug('Incoming request to %s:%d was rejected by the SSH server.' %
                     (self.chain_host, self.chain_port))
             return
 
         logger.debug('Connected!  Tunnel open %r -> %r -> %r' % (self.request.getpeername(),
                                                             chan.getpeername(), (self.chain_host, self.chain_port)))
         while True:
             r, w, x = select.select([self.request, chan], [], [])
             if self.request in r:
                 data = self.request.recv(1024)
                 if len(data) == 0:
                     break
                 chan.send(data)
             if chan in r:
                 data = chan.recv(1024)
                 if len(data) == 0:
                     break
                 self.request.send(data)
         chan.close()
         self.request.close()
         logger.debug('Tunnel closed ')
 
 
 def forward_tunnel(local_port, remote_host, remote_port, transport):
     # this is a little convoluted, but lets me configure things for the Handler
     # object.  (SocketServer doesn't give Handlers any way to access the outer
     # server normally.)
     class SubHander (Handler):
         chain_host = remote_host
         chain_port = remote_port
         ssh_transport = transport
     ForwardServer(('127.0.0.1', local_port), SubHander).serve_forever()
 
 
 __all__ = ['forward_tunnel']