def package_files
      Dir.mktmpdir {|tmpdir|
        @stemcell_files.flatten.each {|file| FileUtils.cp(file, tmpdir) if file && File.exists?(file) } # only copy files that are not nil
        Dir.chdir(tmpdir) do
          @logger.info("Package #@stemcell_files to #@target ...")
          sh "tar -czf #@target *", {:on_error => "unable to package #@stemcell_files into a stemcell"}
        end
      }
      @target
    end
def package_files
      Dir.mktmpdir {|tmpdir|
        @stemcell_files.flatten.each {|file| FileUtils.cp(file, tmpdir) if file && File.exists?(file) } # only copy files that are not nil
        Dir.chdir(tmpdir) do
          @logger.info("Package #@stemcell_files to #@target ...")
          sh "tar -czf #@target *", {:on_error => "unable to package #@stemcell_files into a stemcell"}
        end
      }
      @target
    end
Package all files specified as arguments into a tar. The output file is specified by the :target option