def get_child_text(self, name, strict=True):
        """Extract text of a child element. If strict, and child element is
        not present, raises InvalidXMLError and otherwise returns
        None.

        """
        if strict:
            try:
                return self.element.find('s3:{}'.format(name), _S3_NS).text
            except _ETREE_EXCEPTIONS as error:
                raise InvalidXMLError(
                    ('Invalid XML provided for "{}" - erroring tag <{}>. '
                     'Message: {}').format(self.root_name, name, error.message)
                )
        else:
            return self.element.findtext('s3:{}'.format(name), None, _S3_NS)
Extract text of a child element. If strict, and child element is
        not present, raises InvalidXMLError and otherwise returns
        None.