message: Print the content of the output file when failed to start a lang's server.
diff: @@ -131,6 +131,11 @@ def _server_cmd(lang: str, port: int) -> List[str]:
  return [server_path, '--port', '%d' % port]
  +def _get_file_content(filename: str) -> str:
  + with open(filename, 'r') as f:
  + return f.read()
  +
  +
  class _TestingServers():
  """TestingServers starts up testing gRPC servers and returns service stubs."""
  @@ -178,9 +183,10 @@ class _TestingServers():
  except Exception as e:
  logging.info('Timeout while connecting to server %s', lang)
  self._server[lang].kill()
  - out, err = self._server[lang].communicate()
  - raise RuntimeError('Could not start %s server, output=%s, err=%s' %
  - (lang, out, err)) from e
  + _, _ = self._server[lang].communicate()
  + raise RuntimeError(
  + 'Could not start %s server, output=%s' %
  + (lang, _get_file_content(self._output_file[lang].name))) from e
  self._metadata_stub[lang] = testing_api_pb2_grpc.MetadataStub(
  self._channel[lang])
  self._keyset_stub[lang] = testing_api_pb2_grpc.KeysetStub(
  