This happens during cookbook upload to chef server and is due to unicode characters in README.md (at least in my case)
Ridley::CookbookResource crashed! Encoding::InvalidByteSequenceError: "\xE2" on US-ASCII
I’ve used the following command to list offending characters in README.md. Then removed with gedit, resaved and…. upload success!
grep --color='auto' -P -n "[\x80-\xFF]" README.md
Full stack here: http://fpaste.org/51397/
Reported, here: https://github.com/RiotGames/berkshelf/issues/708