Make isascii python 3.6 compatible
Make isascii python 3.6 compatible

dhomeier/astropy,larrybradley/astropy,mhvk/astropy,lpsinger/astropy,mhvk/astropy,saimn/astropy,mhvk/astropy,pllim/astropy,larrybradley/astropy,astropy/astropy,MSeifert04/astropy,larrybradley/astropy,dhomeier/astropy,mhvk/astropy,larrybradley/astropy,stargaser/astropy,dhomeier/astropy,StuartLittlefair/astropy,stargaser/astropy,astropy/astropy,mhvk/astropy,lpsinger/astropy,pllim/astropy,saimn/astropy,MSeifert04/astropy,lpsinger/astropy,lpsinger/astropy,pllim/astropy,lpsinger/astropy,dhomeier/astropy,saimn/astropy,StuartLittlefair/astropy,dhomeier/astropy,stargaser/astropy,larrybradley/astropy,MSeifert04/astropy,saimn/astropy,StuartLittlefair/astropy,saimn/astropy,aleksandr-bakanov/astropy,stargaser/astropy,aleksandr-bakanov/astropy,aleksandr-bakanov/astropy,aleksandr-bakanov/astropy,MSeifert04/astropy,pllim/astropy,astropy/astropy,astropy/astropy,StuartLittlefair/astropy,pllim/astropy,StuartLittlefair/astropy,astropy/astropy