added test for usefulness of error message when getting frame components
added test for usefulness of error message when getting frame components

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