First Gem fails to install

Ruby 1.8.7 on CentOS 6.

# As user
gem build ct_character_generator-0.0.1.gemspec
WARNING: no description specified
WARNING: no rubyforge_project specified
WARNING: deprecated autorequire specified
   Successfully built RubyGem
   Name: CT_Character_Generator
   Version: 0.0.1
   File: CT_Character_Generator-0.0.1-unknown.gem

# As root
gem install CT_Character_Generator-0.0.1-unknown.gem
ERROR: While executing gem ... (Gem::Exception)
     Unable to find spec for #<Gem::NameTuple CT_Character_Generator, 0.0.1, unknown>

# gemspec file, format copied from the Pickaxe book, 1st edition
require 'rubygems'

SPEC = Gem::Specification.new do |s|
  s.name = "CT_Character_Generator"
  s.version = "0.0.1"
  s.author = "Leam Hall"
  s.email = "leamhall@gmail.com"
  s.homepage = "https://github.com/LeamHall/CT_Character_Generator"
  s.platform = "Gem::Platform::RUBY"
  s.summary = "Generates Classic Traveller Characters."
  candidates = Dir.glob("{bin,docs,lib,test,data}/**/*")
  s.files = candidates.delete_if do |item|
    item.include?(".git") ||
    item.include?(".gitignore") ||
    item.include?(".rspec")
  end
  s.require_path = "lib"
  s.autorequire = "chargen"
  s.test_file = "test/ts_CT_Character_Generator.rb"
  s.has_rdoc = false
  s.add_dependency("json" , ">= 0")
  s.add_dependency("sqlite3" , ">= 0")
end