Hmmm, in your original description you say that the 'generator.__next__' documentation should be changed, but in the patch the note applies to all generator methods.  From looking at the code it seems that the patch is correct and that '__next__', 'send', 'throw', and 'close' can all raise the "already executing" exception via 'gen_send_ex'.  Documenting this behavior seems reasonable, but you should probably mention what exception gets raises.

BTW, you don't need to make the Misc/NEWS changes a part of your patches.  A core dev will write that for you and since Misc/NEWS is changed so much it might conflict and make patches harder to apply across similar branches (say 3.2 and 3.3).