There are still about 10 places where file is not explicitly closed and FD release is dependent on GC model. Is a patch from me welcome?

I fail to install Twisted under PyPy, because am getting "too many open files" error. They are obviously not closed

I'm being pessimistic here and ensuring setuptools closes all files immediately 
when done with them, in particular for Python VMs that don't use reference 
counting GC.

Those VMs may not GC/close those files until later, and open file handles are 
particularly bad on Windows (you can't delete a file that's in use).

This is of low priority