[foxy backport] Add ostream test for FutureReturnCode (#1327) (#1393)

* Remove deprecated executor::FutureReturnCode APIs. (#1327)

While we are here, add in another test for the stream operator for future_return_code.cpp

Signed-off-by: Chris Lalancette <clalancette@openrobotics.org>

* Revert removing deprecated API

Signed-off-by: Stephen Brawner <brawner@gmail.com>

Co-authored-by: Chris Lalancette <clalancette@openrobotics.org>

rclcpp/test/rclcpp/test_future_return_code.cpp

@@ -1,4 +1,4 @@
-// Copyright 2015 Open Source Robotics Foundation, Inc.
+// Copyright 2020 Open Source Robotics Foundation, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -14,6 +14,7 @@
 
 #include <gtest/gtest.h>
 
+#include <sstream>
 #include <string>
 
 #include "rclcpp/future_return_code.hpp"
@@ -32,3 +33,10 @@ TEST(TestFutureReturnCode, to_string) {
   EXPECT_EQ(
     "Unknown enum value (100)", rclcpp::to_string(rclcpp::FutureReturnCode(100)));
 }
+
+TEST(FutureReturnCode, ostream) {
+  std::ostringstream ostream;
+
+  ostream << rclcpp::FutureReturnCode::SUCCESS;
+  ASSERT_EQ("SUCCESS (0)", ostream.str());
+}