The attached file sp-3.py simulates what I think is happening within the
subprocess module. Note that the OS handle is duplicated to allow
inheritance and then left unclosed on failure. If it is explicitly
closed, the file can be removed.

There is no hope of closing the file handle since it was local to the
__init__ method which failed but was not closed before exit and is now
inaccessible.

On the surface, the obvious fix would be a try/except block around the
CreateProcess call (or its caller) which would then release whatever
handles were needed. I'll try to get the time to put a patch together,
but it would be useful to have confirmation of my theory.