assert_ruby_file_exists

# File tools/profile, line 70
      def assert_ruby_file_exists(path)
        fail Error.new("No such file") unless File.exist?(path)
        fail Error.new("#{path} is a directory") if File.directory?(path)
        ruby_extension = File.extname(path) == ".rb"
        ruby_executable = File.open(path, "rb") { |f| f.readline } =~ [/\A#!.*ruby/]
        fail Error.new("Not a ruby file") unless ruby_extension || ruby_executable
      end