Returns XML root.

def get_xml_root(xml_file):
    """Returns XML root."""
    try:
        xml_root = etree.parse(os.path.expanduser(xml_file), NO_BLANKS_PARSER).getroot()
    # pylint: disable=broad-except
    except Exception as err:
        raise Dump2PolarionException("Failed to parse XML file '{}': {}".format(xml_file, err))
    return xml_root