<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def _get_xml(xml_str):
    '''
    Intrepret the data coming from opennebula and raise if it's not XML.
    '''
    try:
        xml_data = etree.XML(xml_str)
    # XMLSyntaxError seems to be only available from lxml, but that is the xml
    # library loaded by this module
    except etree.XMLSyntaxError as err:
        # opennebula returned invalid XML, which could be an error message, so
        # log it
        raise SaltCloudSystemExit('opennebula returned: {0}'.format(xml_str))
    return xml_data