I solve the problem
Unknown option 'francais' by installing the missing language package:
sudo apt-get install texlive-lang-european
Now, encounter the problem
Unknown language 'french', the detailed error info is as follows:
! Package babel Error: Unknown language `french'. Either you have (babel) misspelled its name, it has not been installed, (babel) or you requested it in a previous run. Fix its name, (babel) install it or just rerun the file, respectively.