Added another error message to initial_setup.py.
Added another error message to initial_setup.py.

TheTypoMaster/evennia,ypwalter/evennia,ergodicbreak/evennia,mrkulk/text-world,ypwalter/evennia,feend78/evennia,feend78/evennia,titeuf87/evennia,TheTypoMaster/evennia,emergebtc/evennia,emergebtc/evennia,mrkulk/text-world,ypwalter/evennia,titeuf87/evennia,jamesbeebop/evennia,shollen/evennia,titeuf87/evennia,jamesbeebop/evennia,emergebtc/evennia,shollen/evennia,titeuf87/evennia,TheTypoMaster/evennia,jamesbeebop/evennia,feend78/evennia,ergodicbreak/evennia,feend78/evennia,ergodicbreak/evennia,mrkulk/text-world,mrkulk/text-world