> Having spent a few days pondering this after Ezio first mentioned the
> concept to me on IRC, I'm rejecting this on the basis of "not every 3 
> line function needs to be in the standard library".

When I first mentioned this to Nick on IRC, the implementation of itercm() was a not-so-trivial function that called __enter__/__exit__ manually while catching StopIteration.  It only occurred to me while posting this issue, that the same could be achieved with a simple `yield from` in a `with`.
I also didn't realize that the __exit__ called in case of error in the attached example was triggered by the garbage collector.
I therefore agree that a somewhat obscure and non-deterministic three-liner doesn't belong in the standard library.  Thanks everyone for the feedback!