rdiff-backup: "Warning: Extended Attributes file not found"

My backup cronjobs suddenly started mailing me weird rdiff-backup warnings, like this:

Warning: Extended Attributes file not found
Warning: Extended Attributes file not found
Warning: Access Control List file not found
Warning: Extended Attributes file not found
Warning: Access Control List file not found
Warning: Extended Attributes file not found
Warning: Access Control List file not found
Warning: Extended Attributes file not found
Warning: Extended Attributes file not found
Warning: Extended Attributes file not found

Confusing, eh? Turns out the reason is that I recently installed the python-pylibacl and python-pyxattr packages. The rdiff-backup package in Debian recommends, but does not depend on these packages. If present, rdiff-backup stores extended attributes in destination/rdiff-backup-data/extended_attributes.*

So yes, these warnings are safe to ignore, if you just installed the above packages.