message: Add hint that list should be empty
diff: @@ -688,7 +688,7 @@ style:
  @echo "Checking usage of cout and cerr."
  @-(grep cout */*.?pp | grep -v examples/ | grep -v general/globals | grep -v cerrno)|| true
  @-(grep cerr */*.?pp | grep -v examples/ | grep -v general/globals | grep -v cerrno)|| true
  -
  + @echo "This list should be empty!!"
  # Print the contents of a makefile variable, e.g.: 'make print-MFEM_LIBS'.
  print-%:
  