Hanged if firefox process is defunct

[parmegv]

2016-04-25 21:25:51,183 - INFO - *** Visit #3 to http://norton.com ***
2016-04-25 21:25:53,400 - INFO - dumpcap -P -a duration:120 -a filesize:40000 -i eth0 -s 0 -f 'tcp and not host 127.0.0.1 and not tcp port 22 and not tcp port 20' -w /home/ubuntu/tor-browser-crawler/results/160425_194146/0_21_3/capture.pcap
2016-04-25 21:26:17,108 - INFO - Dumpcap killed. Capture size: 1954898 Bytes /home/ubuntu/tor-browser-crawler/results/160425_194146/0_21_3/capture.pcap
2016-04-25 21:26:22,437 - INFO - Filtering packets without a guard IP.
2016-04-25 21:26:23,212 - INFO - *** Visit #4 to http://norton.com ***
2016-04-25 21:26:25,424 - INFO - dumpcap -P -a duration:120 -a filesize:40000 -i eth0 -s 0 -f 'tcp and not host 127.0.0.1 and not tcp port 22 and not tcp port 20' -w /home/ubuntu/tor-browser-crawler/results/160425_194146/0_21_4/capture.pcap
2016-04-25 21:26:48,185 - INFO - Dumpcap killed. Capture size: 1975077 Bytes /home/ubuntu/tor-browser-crawler/results/160425_194146/0_21_4/capture.pcap
2016-04-25 21:26:53,416 - INFO - Filtering packets without a guard IP.
2016-04-25 21:26:54,134 - INFO - *** Visit #5 to http://norton.com ***
Traceback (most recent call last):
File "./bin/tbcrawler.py", line 16, in
run()
File "/home/ubuntu/tor-browser-crawler/tbcrawler/pytbcrawler.py", line 68, in run
crawler.crawl(job)
File "/home/ubuntu/tor-browser-crawler/tbcrawler/crawler.py", line 28, in crawl
self.do_batch()
File "/home/ubuntu/tor-browser-crawler/tbcrawler/crawler.py", line 45, in __do_batch
self.__do_instance()
File "/home/ubuntu/tor-browser-crawler/tbcrawler/crawler.py", line 52, in __do_instance
with self.driver.launch():
File "/usr/lib/python2.7/contextlib.py", line 17, in __enter
return self.gen.next()
File "/home/ubuntu/tor-browser-crawler/tbcrawler/pytbcrawler.py", line 205, in launch
self.driver = TorBrowserDriver(_self.args, *_self.kwargs)
File "/home/ubuntu/tor-browser-crawler/src/tbselenium/tbselenium/tbdriver.py", line 68, in init
timeout=60)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/firefox/webdriver.py", line 107, in init
keep_alive=True)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 91, in init
self.start_session(desired_capabilities, browser_profile)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 173, in start_session
'desiredCapabilities': desired_capabilities,
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 231, in execute
response = self.command_executor.execute(driver_command, params)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/remote_connection.py", line 395, in execute
return self._request(command_info[0], url, body=data)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/remote_connection.py", line 426, in _request
resp = self._conn.getresponse()
File "/usr/lib/python2.7/httplib.py", line 1051, in getresponse
response.begin()
File "/usr/lib/python2.7/httplib.py", line 415, in begin
version, status, reason = self._read_status()
File "/usr/lib/python2.7/httplib.py", line 371, in _read_status
line = self.fp.readline(_MAXLINE + 1)
File "/usr/lib/python2.7/socket.py", line 476, in readline
data = self._sock.recv(self._rbufsize)
socket.error: [Errno 104] Connection reset by peer
ubuntu@ip-172-31-29-121:~/tor-browser-crawler$

It got stuck, and I killed the firefox process.

The hard timeout should stop that visit, but it doesn't.