$ gem update --system
Updating rubygems-update
WARNING:  You don't have /home/fowl/.gem/ruby/1.9.1/bin in your PATH,
	  gem executables will not run.
Successfully installed rubygems-update-1.8.21
ERROR:  While executing gem ... (Errno::ENOENT)
    No such file or directory - /usr/lib/ruby/gems/1.9.1/gems/rubygems-update-1.8.21