I had this problem "https://stackoverflow.com/questions/19612185/unable-to-install-cocoapods-gem-from-rubygems-org-bad-response-backend-read-e" and as one of the solutions said I tried to remove/add rubygem sources. It was removed without problem, but when I tried to add it back it's giving me an error. Here's my action on terminal and response:
$ gem sources --add https://rubygems.org/
Error fetching https://rubygems.org/:
server did not return a valid file (https://rubygems.org/specs.4.8.gz)
Does anyone know what is the problem?