logcheck pam_xdg_support should be ignored

On a Ubuntu 12.10 system running Gnome3 (gnome-shell), logcheck keeps sending emails about this common task:

    Mar 20 07:36:59 my-system-name su[6390]: pam_xdg_support(su:session): Called as non-root.

Adding this to /etc/logcheck/violations.ignore.d/logcheck-su eliminates this message:

    ^\w{3} [ :0-9]{11} [._[:alnum:]-]+ su\[[0-9]+\]: pam_xdg_support\(su:session\): Called as non-root.