modify to maintain a list of optional package names, and make the HAS_ names separately
modify to maintain a list of optional package names, and make the HAS_ names separately

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