code: def _RunScript(self, metadata_key, metadata_script):
      
      process = subprocess.Popen(
          metadata_script, shell=True,
          executable=self.default_shell,
          stderr=subprocess.STDOUT, stdout=subprocess.PIPE)
      while True:
        for line in iter(process.stdout.readline, b''):
          message = line.decode('utf-8', 'replace').rstrip('\n')
          if message:
            self.logger.info('%s: %s', metadata_key, message)
        if process.poll() is not None:
          break
      self.logger.info('%s: Return code %s.', metadata_key, process.returncode)
docs: Run a script and log the streamed script output.
  
      Args:
        metadata_key: string, the key specifing the metadata script.
        metadata_script: string, the file location of an executable script.