I downloaded two gem files: Sass-3.3.7.gem
& compass-0.12.6.gem
I ran gem install --local Sass-3.3.7.gem
which it installe
Compass 0.12.6 apparently depends on sass ~>3.2.19, which means that the version of sass should be bigger than 3.2 and smaller than 3.3, so basically compass needs sass 3.2.x. You have two options.