Does not work with newer xml.etree

[osynge]

Fails with:

(py38) $/home/HOME/.local/bin/vjunit  -f  ./test-results/pytest-report-ordered-py39.xml 
Traceback (most recent call last):
  File "/home/HOME/.local/bin/vjunit", line 8, in <module>
    sys.exit(main())
  File "/home/HOME/.local/lib/python3.9/site-packages/vjunit/__main__.py", line 13, in main
    vjunit.convert(args.file, args.output)
  File "/home/HOME/.local/lib/python3.9/site-packages/vjunit/vjunit.py", line 80, in convert
    testsuites = self.parse(path)
  File "/home/HOME/.local/lib/python3.9/site-packages/vjunit/vjunit.py", line 22, in parse
    return self.parse_content(self._load_file(path))
  File "/home/HOME/.local/lib/python3.9/site-packages/vjunit/vjunit.py", line 32, in parse_content
    children = testcase.getchildren()
AttributeError: 'xml.etree.ElementTree.Element' object has no attribute 'getchildren'