message: Check tink version of testing servers on startup.
diff: @@ -217,13 +217,24 @@ def start(output_files_prefix: Text) -> None:
  global _ts
  _ts = _TestingServers(output_files_prefix)
  + versions = {}
  for lang in LANGUAGES:
  response = _ts.metadata_stub(lang).GetServerInfo(
  testing_api_pb2.ServerInfoRequest())
  if lang != response.language:
  raise ValueError(
  'lang = %s != response.language = %s' % (lang, response.language))
  - logging.info('server_info:\n%s', response)
  + if response.tink_version:
  + versions[lang] = response.tink_version
  + else:
  + logging.warning('server in lang %s has no tink version.', lang)
  + unique_versions = list(set(versions.values()))
  + if not unique_versions:
  + raise ValueError('tink version unknown')
  + if len(unique_versions) > 1:
  + raise ValueError('tink_version in testing servers are inconsistent: %s' %
  + versions)
  + logging.info('Tink version: %s', unique_versions[0])
  def stop() -> None:
  