Raise proper error if attr is not a column name
Raise proper error if attr is not a column name

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