Failed to work AsciidoctorDiagram fomular for homebrew

asciidoctor-diagram.rb

class AsciidoctorDiagram < Formula
  desc "Asciidoctor Diagram is a set of Asciidoctor extensions that enable you to add diagrams, which you describe using plain text, to your AsciiDoc document."
  homepage "https://asciidoctor.org/"
  url "https://github.com/asciidoctor/asciidoctor-diagram/archive/v1.5.10.tar.gz"
  sha256 "77051e3b203a8782a229d330e9248703c22af992b80e17caf77ae79fb1c8aaf5"

  bottle do
    cellar :any_skip_relocation
    sha256 "6a72d25edb4069881295094ed39f7bc0d3b1aeef3cb8dbe55df06291b7c87330" => :mojave
    sha256 "b31c91e2218a7d877243bf973519644552bfa6775f0afb9cee9e7964450be7a1" => :high_sierra
    sha256 "56ff379da06e486b925ac6bfc1459a8810243c54118a4088b70b3af463a26851" => :sierra
    sha256 "b2cada743cbac6d0f36ea211cc9bbf6b0fba53264ff04fc7be95141ddbc2a2d1" => :el_capitan
  end

  def install
    ENV["GEM_HOME"] = libexec
    system "gem", "build", "asciidoctor-diagram.gemspec"
    system "gem", "install", "asciidoctor-diagram-#{version}.gem"
    bin.install Dir[libexec/"bin/*"]
    bin.env_script_all_files(libexec/"bin", :GEM_HOME => ENV["GEM_HOME"])
  end
end