I'm seeing this in an execution now:
Spoiler:
File "calibre_plugins.goodreads_sync.core", line 486, in search_for_goodreads_books
File "calibre_plugins.goodreads_sync.core", line 157, in _request_get
File "calibre_plugins.goodreads_sync.httplib2.__init__" , line 1470, in request
File "calibre_plugins.goodreads_sync.httplib2.__init__" , line 1270, in _request
File "calibre_plugins.goodreads_sync.httplib2.__init__" , line 1470, in request
File "calibre_plugins.goodreads_sync.httplib2.__init__" , line 1222, in _request
File "calibre_plugins.goodreads_sync.httplib2.__init__" , line 1158, in _conn_request
File "calibre_plugins.goodreads_sync.httplib2.__init__" , line 939, in connect
SSLHandshakeError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:590)
I guess goodreads has begun to use https.