message: add proper protection for opening alien files
diff: @@ -432,8 +432,8 @@ void AliAnalysisTaskElectronEfficiencyV2::UserCreateOutputObjects(){
  fResoFile = TFile::Open(fResoFilename.c_str());
  }
  - if (!fResoFile->IsOpen()) {
  - AliError(Form("Could not open file %s", fResoFilename.c_str()));
  + if (!fResoFile) {
  + AliFatal(Form("Could not open file %s", fResoFilename.c_str()));
  }
  fArrResoPt = (TObjArray *)fResoFile->Get("RelPtResArrCocktail");
  fArrResoEta = (TObjArray *)fResoFile->Get("EtaResArrVsPt");
  @@ -454,8 +454,8 @@ void AliAnalysisTaskElectronEfficiencyV2::UserCreateOutputObjects(){
  std::cout << "Copy cocktail weighting from Alien" << std::endl;
  fCocktailFile = TFile::Open(fCocktailFilename.c_str());
  }
  - if (!fCocktailFile->IsOpen()) {
  - AliError(Form("Could not open file %s", fCocktailFilename.c_str()));
  + if (!fCocktailFile) {
  + AliFatal(Form("Could not open file %s", fCocktailFilename.c_str()));
  }
  if (fCocktailFile){
  