make unit checking more concise
make unit checking more concise

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