> The idea which this issue represents is not rejected.  It is a good one, we found a need for it during the dev sprint last September.

Well, not everybody thinks it is a good one.  I, for instance, don't think it's a good idea, so it is at least one "-1".  I saw Serhiy was unsure about this new feature too, so maybe there are two "-1"s; I don't know.  So I kindly ask(-ed) for it to be openly discussed on python-dev, instead of making a unilateral decision.

The problem with the current design is that GC can become enabled inside the 'with' block at any time:

    with gc.ensure_disabled():
        # gc.is_enabled() might be True !

The GC can become enabled from another OS thread, as we have one GC per process.  Adding a locking mechanism might be tricky in terms of implementation, and risky in terms of allowing people to accidentally have a deadlock or something.  In short, I don't see any way to make this context manager to work reliably in CPython.

Therefore, I think that the best location for a helper like this would be some unittesting helpers collection, as it can work only under some very specific conditions.  The core 'gc' module is currently a collection of low-level primitives.  I think we need a very solid motivation to add a core GC function that works unreliably and is suitable only for unittesting (at best).  

Maybe I'm completely wrong here, in which case I would love to be proved wrong and not just ignored.