that provide a somewhat more uniform interface to getting values.

This is from SF patch #453691.

Code by Evan Simpson.

class FieldStorage: this patch changes read_lines() and co. to use a
StringIO() instead of a real file.  The write() calls are redirected
to a private method that replaces it with a real, external file only
when it gets too big (> 1000 bytes).

This avoids problems in forms using the multipart/form-data encoding
with many fields.  The original code created a temporary file for
*every* field (not just for file upload fields), thereby sometimes
exceeding the open file limit of some systems.

Note that the simpler solution "use a real file only for file uploads"
can't be used because the form field parser has no way to tell which
fields correspond to file uploads.

It's *possible* but extremely unlikely that this would break someone's
code; they would have to be stepping way outside the documented
interface for FieldStorage and use f.file.fileno(), or depend on
overriding make_file() to return a file-like object with additional
known properties.

(Excluding the logging stuff, which doesn't lend itself to use via
"from cgi import *" -- it manipulates globals.)

/usr/local/bin/python and not #! /usr/bin/env python.

added test script and expected output file as well
this closes patch 103297.
__all__ attributes will be added to other modules without first submitting
a patch, just adding the necessary line to the test script to verify
more-or-less correct implementation.