message: TensorFlowTestCase.assertProtoEquals: Leave msg alone if None
  Previously, it was changed to "".
diff: @@ -2176,7 +2176,6 @@ class TensorFlowTestCase(googletest.TestCase):
  message: the message to validate.
  msg: Optional message to report on failure.
  """
  - msg = msg if msg else ""
  if isinstance(expected_message_maybe_ascii, type(message)):
  expected_message = expected_message_maybe_ascii
  self._AssertProtoEquals(expected_message, message, msg=msg)
  @@ -2188,8 +2187,8 @@ class TensorFlowTestCase(googletest.TestCase):
  descriptor_pool=descriptor_pool.Default())
  self._AssertProtoEquals(expected_message, message, msg=msg)
  else:
  - assert False, ("Can't compare protos of type %s and %s. %s" %
  - (type(expected_message_maybe_ascii), type(message), msg))
  + assert False, ("Can't compare protos of type %s and %s." %
  + (type(expected_message_maybe_ascii), type(message)))
  def assertProtoEqualsVersion(
  self,
  