Thank you NiLuJe!
https://www.mobileread.com/forums/showpost.php?p=3787627&postcount=407

LibrarianSync FIX!
Current python version to be fixed is: kindle-python-0.15.N-r15585.tar.xz


/mnt/us/python/lib/python2.7/site-packages/requests/models.py:

add this lines after line 395:
        if is_py2:
            host = unicode(host)
Copy EXACTLY from the very beginning of the first line, with all white spaces (NOT tab spaces). See screenshot.
It should match 'if's in the file. 