Fix failing doc tests.
Fix failing doc tests.

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