In 1b555dbf (py2/py3: Make Products code compatible with both python2
and python3 (nexedi/erp5!1751)., 2024-07-16) we changed the code in a
way that on python2 it would first node text to a python2 str and only
later convert it to unicode, but setting text to a str during the first
step can fail with:

    ValueError: All strings must be XML compatible: Unicode or ASCII, no NULL bytes or control characters

This change to set directly unicode on py2.