Thanks smlewis for your advice, but it looked like that could not solve my problem.
I have confirmed and found my new one in the list, but because it went so fast, I could not copy the line. I saw it showed like ….sucessfully patched cysmtsl.param and like adding mtsl and amino-ethyl to cys…, so the params file I think is OK and feeded.
And the error was still
apps.backrub: Processing xxx.pdb…
core.io.pdb.file_data: [ WARNING ] discarding 5 atoms at position xxx in file xxx.pdb. Best match rsd_type: CYS
core.pack.task.ResfileReader: Unable to add non-canonical amino acid CYSMTSL because it is not in the ResidueTypeSet for residue xx.
ERROR:: Exit from: src/core/pack/task/ResfileReader.cc line: 1195