fails:Net::FTP#site sends the SITE command with the passed argument to the server
fails:Net::FTP#site returns nil
fails:Net::FTP#site does not raise an error when the response code is 202
fails:Net::FTP#site raises a Net::FTPPermError when the response code is 500
fails:Net::FTP#site raises a Net::FTPPermError when the response code is 501
fails:Net::FTP#site raises a Net::FTPTempError when the response code is 421
fails:Net::FTP#site raises a Net::FTPPermError when the response code is 530
