Plugin using own gem

Thanks, gave it a go but get the following error message:

/home/kiffin/.rvm/rubies/ruby-2.3.1/lib/ruby/2.3.0/rubygems/dependency.rb:319:in `to_specs': Could not find 'rubyzip' (~> 1.1.6) among 186 total gem(s) (Gem::LoadError)