Changes to setup_helpers.py from astropy/astropy#2223
Changes to setup_helpers.py from astropy/astropy#2223

bsipocz/astropy-helpers,dpshelio/astropy-helpers,bsipocz/astropy-helpers,embray/astropy_helpers,larrybradley/astropy-helpers,embray/astropy_helpers,astropy/astropy-helpers,dpshelio/astropy-helpers,larrybradley/astropy-helpers,embray/astropy_helpers,embray/astropy_helpers,larrybradley/astropy-helpers,Cadair/astropy-helpers,astropy/astropy-helpers,Cadair/astropy-helpers,bsipocz/astropy-helpers