[bugfix] fix import of httplib after release of requests 2.25
[bugfix] fix import of httplib after release of requests 2.25

Requests v2,25 uses urllib3 1.26, which has removed the export of
httplib from urllib3/response.py.

Use httplib in urllib3.util.response then.

Bug: T267762
Change-Id: I220675cdc61bf508b346c9db2f3f8b5fa9f5d939

wikimedia/pywikibot-core,wikimedia/pywikibot-core