Handle expected deprecation warning when testing build_sphinx
Handle expected deprecation warning when testing build_sphinx

bsipocz/astropy-helpers,Cadair/astropy-helpers,bsipocz/astropy-helpers,bsipocz/astropy-helpers,astropy/astropy-helpers,Cadair/astropy-helpers,dpshelio/astropy-helpers,dpshelio/astropy-helpers,astropy/astropy-helpers