The patch adds a new API method _PyImport_ImportModuleNoLock(const char
*name). It works mostly like PyImport_ImportModule except it does not
block. It tries to fetch the module from sys.modules first and falls
back to PyImport_ImportModule UNLESS the import lock is held by another
thread.

It fixes several issues related to dead locks when a thread uses a
function that imports a module but another thread holds the lock. It
doesn't require static caching of modules.

The patch is against py3k but I can backport it to 2.6.