Fix error message to name the correct starting model.
Fix error message to name the correct starting model.

It was partly superceded by 4b778774084c9c2ffe3e7bf62d0b544da681ec91 that's already been merged. I've merged (and forced)
just the test back onto this branch.

django-import-export/django-import-export,pajod/django-import-export,brillgen/django-import-export,ylteq/dj-import-export,manelclos/django-import-export,pajod/django-import-export,Akoten/django-import-export,PetrDlouhy/django-import-export,ylteq/dj-import-export,rhunwicks/django-import-export,brillgen/django-import-export,brillgen/django-import-export,PetrDlouhy/django-import-export,django-import-export/django-import-export,jnns/django-import-export,ylteq/dj-import-export,piran/django-import-export,daniell/django-import-export,rhunwicks/django-import-export,sergei-maertens/django-import-export,django-import-export/django-import-export,Apkawa/django-import-export,brillgen/django-import-export,Akoten/django-import-export,Apkawa/django-import-export,piran/django-import-export,SalahAdDin/django-import-export,pajod/django-import-export,copperleaftech/django-import-export,PetrDlouhy/django-import-export,manelclos/django-import-export,SalahAdDin/django-import-export,daniell/django-import-export,Akoten/django-import-export,copperleaftech/django-import-export,bmihelac/django-import-export,ericdwang/django-import-export,pajod/django-import-export,jnns/django-import-export,copperleaftech/django-import-export,PetrDlouhy/django-import-export,rhunwicks/django-import-export,copperleaftech/django-import-export,daniell/django-import-export,luto/django-import-export,Apkawa/django-import-export,SalahAdDin/django-import-export,daniell/django-import-export,jnns/django-import-export,ericdwang/django-import-export,bmihelac/django-import-export,ericdwang/django-import-export,sergei-maertens/django-import-export,luto/django-import-export,bmihelac/django-import-export,luto/django-import-export,django-import-export/django-import-export,sergei-maertens/django-import-export,piran/django-import-export,bmihelac/django-import-export,jnns/django-import-export,manelclos/django-import-export