'Asserts that the xml tree does NOT have an element
satisfying `xpath`.
`xml_root` is an etree XML element
`xpath` is an XPath string, such as `\'/foo/bar\'`
`context` is used to print a debugging message'

def assert_no_xpath(self, xml_root, xpath, context_dict):

    self.assert_has_xpath(xml_root, xpath, context_dict, exact_num=0)
