Exit status when there are no files to remove

Hello,

I have a script which performs a backup and then tries to remove all 
increments older than 180 days.  Sometimes, depending on when the script 
has run, there aren't any increments older than 180 days.  rdiff-backup 
then returns with an exit code of 2, which causes the cron job that 
launched the script to send me an email about it, which I don't want. 
Is there a way to stop rdiff-backup from considering the case where no 
increments are older than 180 days as an error?  I thought that --force 
might do it, but no.

Thanks,

Stephen Isard