I'm going to address this issue in parts to make it easier to review and see what is going on.

The first patch I'm uploading shortly here: issue 15403.  That issue I created to address just the "file creation" part of the code.

The approach I'm taking is to keep the file creation code decoupled from the temp directory, sys.path, and import code.  My plan is to address the latter in separate patches by creating or modifying existing test support context managers, as necessary.