ensure that it will be found regardless of the shell PATH. This ensures
that multiprocessing.cpu_count works on default installs of MacOSX.

Emphasize the ['x', 'y'] option for listing field names.  Remove PS2 prompts to make the examples cut-and-pasteable.

longer fails if zlib is not installed. Instead, the zipfile.ZIP_STORED
compression is used to create the ZipFile. Patch by Natalia B. Bidart.

in the _posixsubprocess C extension module it would unintentionally close the fds and raise
an error.