You seem to have the wrong repo URL for some reason. Where did it come from? Probably a mistake on my part publishing that URL somewhere (it's the url to my private staging repo for preparing stuff before I push to github - and obviously not publicly accessible). If you can point me to where you got that url from into your feeds.conf, I'll correct it, of course ;-)
Anyway, just use github URL: https://github.com/plan44/plan44-feed.git , in your feeds.conf (or feeds.conf.default in case you modified that one) then it will work.