fails:Net::FTP#acct writes the ACCT command to the server
fails:Net::FTP#acct returns nil
fails:Net::FTP#acct does not raise any error when the response code is 230
fails:Net::FTP#acct raises a Net::FTPPermError when the response code is 530
fails:Net::FTP#acct raises a Net::FTPPermError when the response code is 500
fails:Net::FTP#acct raises a Net::FTPPermError when the response code is 501
fails:Net::FTP#acct raises a Net::FTPPermError when the response code is 503
fails:Net::FTP#acct raises a Net::FTPTempError when the response code is 421
