If you have a User class and accidentally put the wrong name in the seed, for instance:
rake db:seed_fu outputs
uninitialized constant SeedFu::Runner::Users
Really it should output:
Unknown class Users, Make sure you use the model class name you are trying to seed.
Or maybe if it's plural, you could singularize it:
You are trying to seed with the plural class Users, and you have a User model, please use User in the seed file
I'll likely add this if I get enough use out of the gem