Change _prepare calling sequence for consistency
Change _prepare calling sequence for consistency

pllim/astropy,MSeifert04/astropy,larrybradley/astropy,saimn/astropy,aleksandr-bakanov/astropy,tbabej/astropy,funbaker/astropy,joergdietrich/astropy,saimn/astropy,stargaser/astropy,mhvk/astropy,joergdietrich/astropy,dhomeier/astropy,stargaser/astropy,lpsinger/astropy,astropy/astropy,pllim/astropy,joergdietrich/astropy,larrybradley/astropy,lpsinger/astropy,dhomeier/astropy,bsipocz/astropy,joergdietrich/astropy,tbabej/astropy,larrybradley/astropy,DougBurke/astropy,kelle/astropy,AustereCuriosity/astropy,MSeifert04/astropy,dhomeier/astropy,saimn/astropy,StuartLittlefair/astropy,AustereCuriosity/astropy,kelle/astropy,DougBurke/astropy,StuartLittlefair/astropy,larrybradley/astropy,StuartLittlefair/astropy,lpsinger/astropy,AustereCuriosity/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,mhvk/astropy,funbaker/astropy,bsipocz/astropy,tbabej/astropy,joergdietrich/astropy,aleksandr-bakanov/astropy,DougBurke/astropy,mhvk/astropy,kelle/astropy,saimn/astropy,bsipocz/astropy,tbabej/astropy,astropy/astropy,kelle/astropy,kelle/astropy,MSeifert04/astropy,StuartLittlefair/astropy,mhvk/astropy,dhomeier/astropy,aleksandr-bakanov/astropy,pllim/astropy,stargaser/astropy,astropy/astropy,stargaser/astropy,DougBurke/astropy,funbaker/astropy,mhvk/astropy,astropy/astropy,astropy/astropy,pllim/astropy,StuartLittlefair/astropy,MSeifert04/astropy,AustereCuriosity/astropy,funbaker/astropy,lpsinger/astropy,bsipocz/astropy,AustereCuriosity/astropy,pllim/astropy,tbabej/astropy,dhomeier/astropy,lpsinger/astropy,saimn/astropy