Lock not released when timeout occurs

[erics465]

ucscsdk version: 0.9.0.1
Python version: 3.7.3
Operating System: Debian 10

Description

I was testing error handling with the ucscsdk, especially timeouts when logging in with a handle to UCSC instance. The following code should throw a timeout exception after the default timeout has been exceeded. However, only the first time a handle is being created and times out, the exception is being thrown. After that, further handles just hang forever at the login() method. Digging down the source, it seems that a lock is not released in ucscsession.py when a timeout (or connection refused, etc.) exception occurs (on line 250).

What I Did

Minimal code:

    try:
       handle = UcscHandle(self.creds['hostname'], self.creds['username'], self.creds['password']))
       if handle.last_update_time is None:
           handle.login()
    except Exception as e:
        print(e)
        return

Stacktrace of timeout

Traceback (most recent call last):
  File "/mnt/hgfs/ucsc-exporter/modules/main_collector.py", line 100, in collect
    self.handles[x].login()
  File "/home/eric/.local/lib/python3.7/site-packages/ucscsdk/ucschandle.py", line 117, in login
    return self._login(auto_refresh, force)
  File "/home/eric/.local/lib/python3.7/site-packages/ucscsdk/ucscsession.py", line 475, in _login
    response = self.post_elem(elem)
  File "/home/eric/.local/lib/python3.7/site-packages/ucscsdk/ucscsession.py", line 250, in post_elem
    response_str = self.post_xml(xml_str, dme=dme)
  File "/home/eric/.local/lib/python3.7/site-packages/ucscsdk/ucscsession.py", line 203, in post_xml
    response_str = self.post(uri=ucsm_uri, data=xml_str, read=read)
  File "/home/eric/.local/lib/python3.7/site-packages/ucscsdk/ucscsession.py", line 185, in post
    response = self.__driver.post(uri=uri, data=data, read=read)
  File "/home/eric/.local/lib/python3.7/site-packages/ucscsdk/ucscdriver.py", line 180, in post
    response = opener.open(request, timeout=10)
  File "/usr/lib/python3.7/urllib/request.py", line 525, in open
    response = self._open(req, data)
  File "/usr/lib/python3.7/urllib/request.py", line 543, in _open
    '_open', req)
  File "/usr/lib/python3.7/urllib/request.py", line 503, in _call_chain
    result = func(*args)
  File "/home/eric/.local/lib/python3.7/site-packages/ucscsdk/ucscdriver.py", line 42, in https_open
    return self.do_open(TLS1Connection, req)
  File "/usr/lib/python3.7/urllib/request.py", line 1319, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error timed out>