Chef bootstrap - public key failure

I tried running chef bootstrap using public key on amazon ec2 server, and get some errors:
    ERROR: ArgumentError: invalid option(s): keys_only
Or
   /usr/lib/ruby/1.8/net/ssh.rb:155:in `start': invalid option(s): keys_only (ArgumentError)
well, i don't know if it is a bug, but i create a simple solution for this with a simple script
the following script will allow password, run bootstrap and disallow password