This is probably an #upstream bug, but I just want to have at least a note here. It seems that recently the Python 3.6 builds fail due to urllib3 raising a KeyError (see https://travis-ci.org/xZise/pywikibot-core/builds/71550286#L7189):
```
======================================================================
ERROR: testQueryApiGetter (tests.wikidataquery_tests.TestApiSlowFunctions)
Test that we can actually retreive data and that caching works.
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/travis/build/xZise/pywikibot-core/tests/wikidataquery_tests.py", line 252, in testQueryApiGetter
data = w.query(q)
File "/home/travis/build/xZise/pywikibot-core/pywikibot/data/wikidataquery.py", line 601, in query
data = self.getDataFromHost(fullQueryString)
File "/home/travis/build/xZise/pywikibot-core/pywikibot/data/wikidataquery.py", line 563, in getDataFromHost
resp = http.fetch(url)
File "/home/travis/build/xZise/pywikibot-core/pywikibot/comms/http.py", line 359, in fetch
error_handling_callback(request)
File "/home/travis/build/xZise/pywikibot-core/pywikibot/comms/http.py", line 276, in error_handling_callback
raise request.data
File "/home/travis/build/xZise/pywikibot-core/pywikibot/comms/http.py", line 255, in _http_process
auth=auth, timeout=timeout, verify=True)
File "/home/travis/virtualenv/python3.6-dev/lib/python3.6/site-packages/requests/sessions.py", line 465, in request
resp = self.send(prep, **send_kwargs)
File "/home/travis/virtualenv/python3.6-dev/lib/python3.6/site-packages/requests/sessions.py", line 573, in send
r = adapter.send(request, **kwargs)
File "/home/travis/virtualenv/python3.6-dev/lib/python3.6/site-packages/requests/adapters.py", line 337, in send
conn = self.get_connection(request.url, proxies)
File "/home/travis/virtualenv/python3.6-dev/lib/python3.6/site-packages/requests/adapters.py", line 251, in get_connection
conn = self.poolmanager.connection_from_url(url)
File "/home/travis/virtualenv/python3.6-dev/lib/python3.6/site-packages/requests/packages/urllib3/poolmanager.py", line 139, in connection_from_url
return self.connection_from_host(u.host, port=u.port, scheme=u.scheme)
File "/home/travis/virtualenv/python3.6-dev/lib/python3.6/site-packages/requests/packages/urllib3/poolmanager.py", line 125, in connection_from_host
self.pools[pool_key] = pool
File "/home/travis/virtualenv/python3.6-dev/lib/python3.6/site-packages/requests/packages/urllib3/_collections.py", line 66, in __setitem__
_key, evicted_value = self._container.popitem(last=False)
KeyError: ('https', 'eu.wiktionary.org', 443)
```
Now considering that we sometimes get errors when using wikidataquery it might be that this is the same type of error but just with different symptomes. And usual requests work, although that error message appears relatively often but it only leads to two failures (search for `KeyError: (` and I get more than 100 matches on the Travis build mentioned above).