title: sshtunnel.BaseSSHTunnelForwarderError: Could not establish session to SSH gateway
body: <p>My network architecture (unchangeable):
  <em>pc</em> --ssh--> <em>serv</em> --ssh--> <em>serv_mod</em> --telnet--> <em>serv_submod</em>
  For now, I am trying to use ssh tunneling from <em>pc</em> to <em>serv_mod</em></p>
  
  <p><em>pc</em> <code>'10.42.100.2' 'pc_user' 'pc_pass'</code></p>
  
  <p><em>serv</em> <code>'10.42.100.4' 'serv_user' 'serv_pass'</code></p>
  
  <p><em>serv_mod</em> <code>'127.0.0.1' 'serv_mod_user' 'serv_mod_pass'</code></p>
  
  <p><em>serv_submod</em> <code>telnet 192.168.252.100 2323</code></p>
  
  <p>Now I am trying to access <em>serv_submod</em> from <em>pc</em>, however it overcomes me a bit. I have tried to use ssh tunneler to reach <em>serv_mod</em> first, but I have following error:</p>
  
  <pre><code>sshtunnel.BaseSSHTunnelForwarderError: Could not establish session to SSH gateway
  
  
  
  with SSHTunnelForwarder(
          ('10.42.100.4', 22),
          ssh_username='serv_user',
          ssh_password='serv_pass',
          remote_bind_address=('127.0.0.1', 8080)
      ):
          logger.debug('ssh tunnel estabilished')
          client = paramiko.SSHClient()
          client.load_system_host_keys()
          client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
          client.connect('127.0.0.1', 22)
          client.close()
  </code></pre>
  
  <p>Can you help me solve this issue and maybe suggest proper way to connect 'directly' to <em>serv_submod</em></p>
  
  <p>Thank you in advance</p>