def _GetMetadataUpdate(self, timeout_secs=60):
    try:
      response = self._WaitForUpdate(timeout_secs=timeout_secs)
      response_info = response.info()
      if response_info and response_info.has_key('etag'):
        self.etag = response_info.getheader('etag')
      content = response.read()
      logging.debug('response: %s', content)
      return content
    except urllib2.HTTPError as e:
      if e.code == 404:
        # The metadata server content doesn't exist. Return None.
        # No need to log a warning.
        return None
      # Rethrow the exception since we don't know what it is. Let the
      # top layer handle it.
      raise
    return None
Fetches the content of the metadata server.
dataset/ETHPy150Open GoogleCloudPlatform/compute-image-packages/google-daemon/usr/share/google/google_daemon/desired_accounts.py/DesiredAccounts._GetMetadataUpdate