NiFi: Using xml.etree.ElementTree in Python script

Nifi 1.5.0 I'm try execute this Python Script in ExecuteScript processor:

import java.io
from org.apache.commons.io import IOUtils
from java.nio.charset import StandardCharsets
from org.apache.nifi.processor.io import StreamCallback
import xml.etree.ElementTree as ET

class PyStreamCallback(StreamCallback):
    def __init__(self):
        pass
    def process (self, inputStream, outputStream):
        xmlRaw = IOUtils.toString(inputStream, StandardCharsets.UTF_8)
        tree = ET.fromstring(xmlRaw)
        root = tree.getroot()
        xmlFix = ET.tostring(root, encoding='utf8', method='xml')
        outputStream.write(bytearray(xmlFix))

flowFile = session.get()
if (flowFile != None):
        #callback = PyStreamCallback(flowFile)
        #session.read(flowFile, callback)
        flowFile = session.write(flowFile, PyStreamCallback())
        session.transfer(flowFile, REL_SUCCESS)
        session.commit()

And I have error:

ExecuteScript[id=3c68eecc-0172-1000-ffff-ffff82be9cc3] Failed to process session due to javax.script.ScriptException: org.xml.sax.SAXException: org.xml.sax.SAXException: SAX2 driver class org.apache.xerces.parsers.SAXParser not found
java.lang.ClassNotFoundException: org.apache.xerces.parsers.SAXParser in <script> at line number 21: org.apache.nifi.processor.exception.ProcessException: javax.script.ScriptException: org.xml.sax.SAXException: org.xml.sax.SAXException: SAX2 driver class org.apache.xerces.parsers.SAXParser not found
java.lang.ClassNotFoundException: org.apache.xerces.parsers.SAXParser in <script> at line number 21

xml.etree.ElementTree not supported in Jython or it Nifi configuration error?