Remove try-except-as doc targeted at PY2 from dev guide. [skip appveyor] [docs only]
Remove try-except-as doc targeted at PY2 from dev guide. [skip appveyor] [docs only]

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