Fix fixture issue with pytest 3.7 in test_statistics.py
Fix fixture issue with pytest 3.7 in test_statistics.py

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