message: Accomodate c++ libraries, that don't provide std::string::append(string_view).
diff: @@ -147,9 +147,9 @@ static std::string JoinStatusMessages(
  const std::vector<absl::Status>& statuses) {
  return absl::StrCat(
  "[combined statuses]:\n",
  - absl::StrJoin(statuses, "\n",
  - [](std::string* out, const absl::Status& status) {
  - out->append(status.message());
  + absl::StrJoin(
  + statuses, "\n", [](std::string* out, const absl::Status& status) {
  + out->append(status.message().begin(), status.message().end());
  }));
  }
  