There's an entry that addresses this in the manual's FAQ: https://openflow.stanford.edu/display/ONL/POX+Wiki#POXWiki-Whataretheselogmessagesfromthepacketsubsystem%3F
Solution 2 might work for you except that you might want to change it to CRITICAL instead of WARN since you have a few at ERROR level.
The fact that you've got a couple at ERROR level is actually sort of interesting. And the error message is obviously useless/broken and could be fixed. But it'd also be interesting to know what's causing it. Maybe it's just IPv6? If you wanted to send more info about the problematic DNS packets (or a capture), we might be able to fix that.