➜  ~  rvm rubygems latest-1.8
Retrieving rubygems-1.8.21
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  250k  100  250k    0     0   176k      0  0:00:01  0:00:01 --:--:--  273k
Extracting rubygems-1.8.21 ...
Removing old Rubygems files...
-e:1: Use RbConfig instead of obsolete and deprecated Config.
Installing rubygems-1.8.21 for system ...
Error running 'GEM_PATH=":@global" GEM_HOME="" "/home/tester/.rvm/rubies/system/bin/ruby" "/home/tester/.rvm/src/rubygems-1.8.21/setup.rb"', please read /home/tester/.rvm/log/system/rubygems.install.log
Installation of rubygems did not complete successfully.