I'm trying to install the paperclip plugin with the following command:

ruby script/plugin install git://github.com/thoughtbot/paperclip.git

But I'm getting some errors:

ruby script/plugin install git://github.com/thoughtbot/paperclip.git --force
svn: '/home/app/vendor/plugins' is not a working copy
/usr/lib/ruby/1.8/open-uri.rb:32:in `initialize': No such file or directory - git://github.com/thoughtbot/paperclip.git (Errno::ENOENT)
    from /usr/lib/ruby/1.8/open-uri.rb:32:in `open_uri_original_open'
    from /usr/lib/ruby/1.8/open-uri.rb:32:in `open'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:863:in `fetch_dir'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:857:in `fetch'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:856:in `each'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:856:in `fetch'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:219:in `install_using_http'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:169:in `send'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:169:in `install'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:734:in `parse!'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:732:in `each'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:732:in `parse!'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:447:in `parse!'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:463:in `parse!'
    from ./script/../config/../vendor/rails/railties/lib/commands/plugin.rb:871
    from script/plugin:3:in `require'
    from script/plugin:3

Is it because I'm using a old rails version?