py/runtime: Allow to override builtins.__import__ with Python func.

This patch adds a simple but powerful hook into the import system, in a
CPython compatible way, by allowing to override builtins.__import__.

This does introduce some overhead to all imports but it's minor:
- the dict lookup of __import__ is bypassed if there are no modifications
  to the builtins module (which is the case at start up);
- imports are not performance critical, usually done just at the start of a
  script;
- compared to how much work is done in an import, looking up a value in a
  dict is a relatively small additional piece of work.

0 files changed, 0 insertions, 0 deletions