Test that non-standard units are never written to TUNIT*
Test that non-standard units are never written to TUNIT*

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