Ignore Python3 __pycache__ subdirs (replaces Python2's *.pyc files)
Start testing 'import' from lazily loaded modules
Module.Root(): Add returned root object to sys.modules

This silences the following warning which Python2 throws when the code
being exec-ed attempts a regular 'import' statement.

  RuntimeWarning: Parent module 'root' not found while handling absolute import
Document current issue with relative module imports
WIP: TODO