[shurikkk]

Final update. In _utills.py instead of

python:
try:

    import xml.etree.cElementTree as default_etree

except ImportError:

    import xml.etree.ElementTree as default_etree

I put the direct, non-compiled import 

python:
import xml.etree.ElementTree as default_etree

It is a bit slower, but at least now it works. I still don't know what caused that peculiar error.