'Processes XML <blacklist> nodes into BlacklistEntry objects.
The following information is parsed out:
subnet: The IP, in CIDR notation.
description: (optional)
If there are no errors, the data is loaded into a BlackListEntry object
and added to a list. Upon error, a description of the error is added to
a list and the method terminates.
Args:
node: <blacklist> XML node in dos.xml.'

def ProcessBlacklistNode(self, node):

    tag = xml_parser_utils.GetTag(node)
    if (tag != 'blacklist'):
        self.errors.append(('Unrecognized    node:    <%s>' % tag))
        return
    entry = BlacklistEntry()
    entry.subnet = xml_parser_utils.GetChildNodeText(node, 'subnet')
    entry.description = xml_parser_utils.GetChildNodeText(node, 'description')
    validation = self._ValidateEntry(entry)
    if validation:
        self.errors.append(validation)
        return
    self.blacklist_entries.append(entry)
