message: TensorTracer: Add an explicit error message when trace_dir is not provided.
diff: @@ -141,6 +141,13 @@ class TTParameters(object):
  self.collect_summary_per_core = self.is_flag_on(FLAG_NAME_SUMMARY_PER_CORE)
  self.flush_summaries_with_outside_compile = self.is_flag_on(
  FLAG_FLUSH_SUMMARY)
  + self._check_flag_errors()
  +
  + def _check_flag_errors(self):
  + if self.trace_mode in (TRACE_MODE_SUMMARY, TRACE_MODE_FULL_TENSOR_SUMMARY):
  + if not self.trace_dir:
  + raise ValueError('trace_dir must be explicitly provided in '
  + 'TENSOR_TRACER_FLAGS when summary mode is used.')
  def _get_report_filepath(self):
  """Sets the path of the output report file."""
  