Disclaimer: this bug has been filed in a semi-automated manner.
When emerging the package net-print/cups-1.5.2-r4, the following elog messages are displayed:
* Network browsing for printers is now switched off by default in the config file.
* To (re-)enable it, edit /etc/cups/cupsd.conf and set "Browsing On",
* afterwards re-start or reload cups.
Such messages should only be displayed when the package is upgraded from an old enough package (and possibly for new installs).
These situations can be checked in the ebuild as follows:
if has_version '<net-print/cups-1.0'; then
Or, if the message should also be displayed for new installs:
if !has_version 'net-print/cups' || has_version '<net-print/cups-1.0'; then
Remember to replace 1.0 with the right version number.
See the tracker bug 440214 for more details.