Add the ability to use context.update() as a context manager

[Chris Jerdonek]

The documentation says you can use context.push() as a context manager:

You can also use push() as a context manager to ensure a matching pop() is called.

And the documentation says this about context.update():

This works like push() but takes a dictionary as an argument and pushes that dictionary onto the stack instead of an empty one.

However, update() doesn't seem to act as a context manager like push() does (which I would have found useful). Is there a reason for the difference? If the difference is deliberate, it seems like the documentation should note this difference.

[Tim Graham]

I guess it's probably not a feature that's been requested. See a3e7d73ed7d90d31de46c60d40424267f62e411c for the addition of the context manager to push().

[Tim Graham <timograham@…>]

In 6bfd864:

Fixed #24603 -- Allowed Context.update() to be used as a context manager.

[Chris Jerdonek]

Wow, only six days -- thanks for adding this so quickly!