Add unit test for making sure pop works before loading HDU
Add unit test for making sure pop works before loading HDU

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