Remove python < 3.7 work-around.
Remove python < 3.7 work-around.

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