Sleekxmpp : Failed to import _strptime because the import lockis held by another thread

gistfile1.txt

INFO:sleekxmpp.xmlstream.xmlstream:Negotiating TLS
INFO:sleekxmpp.xmlstream.xmlstream:Using SSL version: 3
ERROR:sleekxmpp.xmlstream.xmlstream:Connection error.
ERROR:sleekxmpp.basexmpp:Failed to import _strptime because the import lockis held by another thread.
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/xmlstream/xmlstream.py", line 1441, in _process
    if not self.__read_xml():
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/xmlstream/xmlstream.py", line 1509, in __read_xml
    self.__spawn_event(xml)
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/xmlstream/xmlstream.py", line 1577, in __spawn_event
    handler.prerun(stanza_copy)
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/xmlstream/handler/callback.py", line 64, in prerun
    self.run(payload, True)
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/xmlstream/handler/callback.py", line 76, in run
    self._pointer(payload)
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/features/feature_starttls/starttls.py", line 64, in _handle_starttls_proceed
    if self.xmpp.start_tls():
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/xmlstream/xmlstream.py", line 859, in start_tls
    cert.verify(self._expected_server_name, self._der_cert)
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/xmlstream/cert.py", line 137, in verify
    not_before, not_after = extract_dates(raw_cert)
  File "/usr/local/lib/python2.7/dist-packages/sleekxmpp/xmlstream/cert.py", line 114, in extract_dates
    not_before = datetime.strptime(not_before, '%y%m%d%H%M%SZ')
ImportError: Failed to import _strptime because the import lockis held by another thread.
INFO:sleekxmpp.xmlstream.xmlstream:Waiting for </stream:stream> from server
INFO:sleekxmpp.xmlstream.xmlstream:Negotiating TLS
INFO:sleekxmpp.xmlstream.xmlstream:Using SSL version: 3
INFO:sleekxmpp.util.sasl.client:SASL: X-OAUTH2: Missing credential: access_token
INFO:sleekxmpp.util.sasl.client:SASL: X-GOOGLE-TOKEN: Missing credential: access_token
INFO:sleekxmpp.features.feature_bind.bind:Node set to: circadianxmpp@gmail.com/circMan^85DF38F7
INFO:sleekxmpp.xmlstream.xmlstream:CERT: Time until certificate expiration: 39 days, 11:52:04.320754