How to use the junitparser.junitparser.JUnitXmlError function in junitparser

def fromfile(cls, filepath):
        """Initiate the object from a report file."""
        tree = etree.parse(filepath)
        root_elem = tree.getroot()
        if root_elem.tag == "testsuites":
            instance = cls()
        elif root_elem.tag == "testsuite":
            instance = TestSuite()
        else:
            raise JUnitXmlError("Invalid format.")
        instance._elem = root_elem
        instance.filepath = filepath
        return instance

def write_xml(obj, filepath=None, pretty=False):
    tree = etree.ElementTree(obj._elem)
    if filepath is None:
        filepath = obj.filepath
    if filepath is None:
        raise JUnitXmlError("Missing filepath argument.")

    if pretty:
        from xml.dom.minidom import parseString

        text = etree.tostring(obj._elem)
        xml = parseString(text)
        with open(filepath, "wb") as xmlfile:
            xmlfile.write(xml.toprettyxml(encoding="utf-8"))
    else:
        tree.write(filepath, encoding="utf-8", xml_declaration=True)

def write_xml(obj, filepath=None, pretty=False):
    tree = etree.ElementTree(obj._elem)
    if filepath is None:
        filepath = obj.filepath
    if filepath is None:
        raise JUnitXmlError("Missing filepath argument.")

    if pretty:
        from xml.dom.minidom import parseString

        text = etree.tostring(obj._elem)
        xml = parseString(text)
        with open(filepath, "wb") as xmlfile:
            xmlfile.write(xml.toprettyxml(encoding="utf-8"))
    else:
        tree.write(filepath, encoding="utf-8", xml_declaration=True)

def result(self):
        """One of the Failure, Skipped, or Error objects."""
        results = []
        for res in POSSIBLE_RESULTS:
            result = self.child(res)
            if result is not None:
                results.append(result)
        if len(results) > 1:
            raise JUnitXmlError("Only one result allowed per test case.")
        elif len(results) == 0:
            return None
        else:
            return results[0]

def fromfile(cls, filepath):
        """Initiate the object from a report file."""
        tree = etree.parse(filepath)
        root_elem = tree.getroot()
        if root_elem.tag == "testsuites":
            instance = cls()
        elif root_elem.tag == "testsuite":
            instance = TestSuite()
        else:
            raise JUnitXmlError("Invalid format.")
        instance._elem = root_elem
        instance.filepath = filepath
        return instance

def result(self):
        """One of the Failure, Skipped, or Error objects."""
        results = []
        for res in POSSIBLE_RESULTS:
            result = self.child(res)
            if result is not None:
                results.append(result)
        if len(results) > 1:
            raise JUnitXmlError("Only one result allowed per test case.")
        elif len(results) == 0:
            return None
        else:
            return results[0]