Ensure that an exception is raised if metadata_conflict is not one of e expected values.
Ensure that an exception is raised if metadata_conflict is not one of e expected values.

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