Observing a hang within SSHClient.connect()

[sanseihappa]

When attempting to connect to sometimes misbehaving SSH server, I am observing a hang during SSHClient.connect(). Using the faulthandler module, it seems to stem from the call to Transport.start_client().

Here is the faulthandler SIGABRT dump:

28-Jun-2016 08:44:47    Thread 0x00007f72f24cc700 (most recent call first):
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/paramiko/packet.py", line 254 in read_all
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/paramiko/packet.py", line 391 in read_message
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/paramiko/transport.py", line 1754 in run
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 810 in __bootstrap_inner
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 783 in __bootstrap
28-Jun-2016 08:44:47    
28-Jun-2016 08:44:47    Thread 0x00007f72f3cdc700 (most recent call first):
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/xxxxxxxxxxx/xxxxxxxxxx.py", line 643 in xxxxxxxxxxxxxx
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 763 in run
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 810 in __bootstrap_inner
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 783 in __bootstrap
28-Jun-2016 08:44:47    
28-Jun-2016 08:44:47    Thread 0x00007f72f1a0a700 (most recent call first):
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/xxxxxxxxxxx/xxxxxxxxxx.py", line 563 in xxxxxxxxxxxxx
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 763 in run
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 810 in __bootstrap_inner
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 783 in __bootstrap
28-Jun-2016 08:44:47    
28-Jun-2016 08:44:47    Thread 0x00007f72f34db700 (most recent call first):
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/xxxxxxxxxxxxxxxxxx/xxxxxxxxxxxxxxxxxxxx.py", line 197 in xxxxxxxxxxxxx
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/xxxxxxxxxxxxxxxxxx/xxxxxxxxxxxxxxxxxxxx.py", line 155 in xxxxxx
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 763 in run
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 810 in __bootstrap_inner
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 783 in __bootstrap
28-Jun-2016 08:44:47    
28-Jun-2016 08:44:47    Current thread 0x00007f72f89d0740 (most recent call first):
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 358 in wait
28-Jun-2016 08:44:47      File "/usr/lib/python2.7/threading.py", line 620 in wait
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/paramiko/transport.py", line 489 in start_client
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/paramiko/client.py", line 338 in connect
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/xxxxxxxxxxxxx/xxxxxxxxxxxx.py", line 141 in xxxxxxx
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/xxxxxxxxxxxxx/xxxxxxxxxxxx.py", line 278 in xxxxxxxxx
28-Jun-2016 08:44:47      File "/mnt/work/test/lib/utils.py", line 774 in xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
28-Jun-2016 08:44:47      File "features/environment.py", line 222 in after_scenario
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/behave/runner.py", line 405 in run_hook
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/behave/model.py", line 919 in run
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/behave/model.py", line 523 in run
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/behave/runner.py", line 483 in run_model
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/behave/runner.py", line 693 in run_with_paths
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/behave/runner.py", line 672 in run
28-Jun-2016 08:44:47      File "/usr/local/lib/python2.7/dist-packages/behave/__main__.py", line 109 in main
28-Jun-2016 08:44:47      File "/usr/local/bin/behave", line 11 in <module>

[bitprophet]

Rolling into the PR!