This comes from glitz removal (bug #330397), as soon as cairo-1.10 gets
stabilized, depclean will try to remove glitz, but removing glitz will
break a lot of apps, needing to rebuild them and, until then, having a
partially broken system.

I then thought on running revdep-rebuild --library libglitz-glx.so.1
BEFORE removing glitz (to prevent breakage), but later I remembered it
wouldn't work as rebuilt packages would link again against
libglitz-glx.so.1.

Then, my idea would the following:

Would be nice if I could tell portage to make compilation think
libglitz-glx.so.1 is not present in real system (maybe sandbox could
prevent its readability inside build environment), and then, I could run
"revdep-rebuild --library libglitz-glx.so.1" before removing glitz and
affected apps would not link to it, allowing me to safely remove glitz
later without having had  a broken system at any time.

What do you think? Thanks