For what it's worth, we are still using our own null context manager function in critical code. We tend to avoid contextlib.ExitStack() for two reasons:

1) it is not immediately clear from looking at the code what ExitStack() means. (Unlike the "contextmanager" decorator, ExitStack is unfamiliar to most developers.)

2) ExitStack's __init__ and __exit__ incur a non-negligible overhead compared to a true do-nothing context manager.

It doesn't surprise me that projects like Tensor Flow introduce their own versions of this decorator. Having said that, I can also understand why it wasn't added. It is certainly possible to live without it, and ExitStack() is a more than acceptable replacement for casual use.