message: core: check result of system call
diff: @@ -9,7 +9,11 @@ class SitlTest : public testing::Test
  protected:
  virtual void SetUp()
  {
  - system("./start_px4_sitl.sh");
  + const int ret = system("./start_px4_sitl.sh");
  + if (ret != 0) {
  + dronecore::LogErr() << "./start_px4_sitl.sh failed, giving up.";
  + abort();
  + }
  // We need to wait a bit until it's up and running.
  std::this_thread::sleep_for(std::chrono::seconds(3));
  }
  @@ -17,6 +21,10 @@ protected:
  {
  // Don't rush this either.
  std::this_thread::sleep_for(std::chrono::seconds(1));
  - system("./stop_px4_sitl.sh");
  + const int ret = system("./stop_px4_sitl.sh");
  + if (ret != 0) {
  + dronecore::LogErr() << "./stop_px4_sitl.sh failed, giving up.";
  + abort();
  + }
  }
  };
  