-- trying a different approach to see if the crash on Windows goes away.

Running a script with PyRun_File -- a Python/C API function -- was probably
the cause for crashes on Windows, because it uses a pointer to a FILE
struct and on windows this struct can be "different and incompatible"
depending on which libc was used to build the program.  This is mentioned in
the Python/C API Ref Manual, chapter 2.

Now we're loading the file contents to a string buffer and using PyRun_String.