Use a subprocess to compile the test Cython module rather than running it in the same process; otherwise Cython gets confused when you try to compile the same module of the same name more than once.  This is fine here since it's not the actual build process that's being tested in these tests.
Use a subprocess to compile the test Cython module rather than running it in the same process; otherwise Cython gets confused when you try to compile the same module of the same name more than once.  This is fine here since it's not the actual build process that's being tested in these tests.

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