asciidoctor-epub3.gemspec in asciidoctor-epub3-1.5.0.alpha.11 vs asciidoctor-epub3.gemspec in asciidoctor-epub3-1.5.0.alpha.12

@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require File.expand_path('lib/asciidoctor-epub3/version', File.dirname(__FILE__))
+require_relative 'lib/asciidoctor-epub3/version'
 require 'open3' unless defined? Open3
 
 Gem::Specification.new do |s|
   s.name = 'asciidoctor-epub3'
   s.version = Asciidoctor::Epub3::VERSION
@@ -15,12 +15,11 @@
   s.authors = ['Dan Allen', 'Sarah White']
   s.email = '[e-mail]'
   s.homepage = 'https://github.com/asciidoctor/asciidoctor-epub3'
   s.license = 'MIT'
 
-  # NOTE required ruby version is informational only; it's not enforced since it can't be overridden and can cause builds to break
-  #s.required_ruby_version = '>= 2.3.0'
+  s.required_ruby_version = '>= 2.3.0'
 
   files = begin
     (result = Open3.popen3('git ls-files -z') {|_, out| out.read }.split %(\0)).empty? ? Dir['**/*'] : result
   rescue
     Dir['**/*']
@@ -29,13 +28,15 @@
   s.executables = %w(asciidoctor-epub3 adb-push-ebook)
   s.test_files = s.files.grep(/^(?:test|spec|feature)\/.*$/)
 
   s.require_paths = ['lib']
 
-  s.add_development_dependency 'rake', '~> 12.3.0'
+  s.add_development_dependency 'rake', '~> 13.0.0'
   s.add_development_dependency 'rspec', '~> 3.9.0'
-  s.add_development_dependency 'rubocop', '~> 0.78.0'
+  s.add_development_dependency 'rubocop', '~> 0.79.0'
   s.add_development_dependency 'rubocop-rspec', '~> 1.37.0'
 
   s.add_runtime_dependency 'asciidoctor', '>= 1.5.3', '< 3.0.0'
+  s.add_runtime_dependency 'epubcheck-ruby', '~> 4.2.2.0'
   s.add_runtime_dependency 'gepub', '~> 1.0.0'
+  s.add_runtime_dependency 'kindlegen', '>= 3.0.3', '<= 3.0.5'
 end