I am using osx 10.8.2 installed ruby 2.0 and.... got this when trying to run \"sudo gem install rails\"
$
I had the same problem with the same OS version. I use rvm and followed the steps in this command:
$ rvm requirements
Following those instructions, I ran:
$ brew update
$ brew tap homebrew/dupes
$ brew install bash curl git
$ brew install autoconf automake apple-gcc42 libtool pkg-config openssl readline libyaml sqlite libxml2 libxslt libksba