[Python-3000] PEP 3121 implemented

[Greg Ewing]

Martin v. Löwis wrote:

>   However, _sre relied on the module already being in
>   sys.modules, as it runs Python code in the init function that already
>   imports the module being initialized.

This issue also potentially affects all Pyrex and Cython
generated modules, which must be free to execute arbitrary
Python code during initialisation, including imports.

-- 
Greg