Make ElementTree work with Python 3.9+
Make ElementTree work with Python 3.9+

Per the python documentation, getchildren() has been deprecated since
3.2:
https://docs.python.org/3.8/library/xml.etree.elementtree.html

This change tries getchildren() first to be  backwards compatible with
Python 2.7 since it is still common as a system default.

yola/opensrs,yola/opensrs