flake8 improvements
flake8 improvements

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