Sorry for the spam, problems with internet connection.
If the runtime dependency is missing, the following error occurs and catfish won't start:
"Error: The required module gi.repository is missing."
I recommend adding dev-python/pygobject:3 to RDEPEND.
With this fixed, the following warning occurs:
Warning: The optional module zeitgeist.client is missing.
But that is only a minor thing and doesn't affect operation.
Fixed in 0.6.3