Am not sure how much we care about this, but parenthesis around tuples stops being optional when there is a variable annotation. 

>>> from typing import Tuple
>>> t = 10, 'hello'                     # Parens not normally required
>>> t: Tuple[int, str] = (10, 'hello')  # Annotated allows parens
>>> t: Tuple[int, str] = 10, 'hello'    # Annotated w/o parens fails
SyntaxError: invalid syntax

Good catch!

I think it was just overlooked rather than a conscious decision (unlike the left hand side, that generated lots of debates)

I will make a PR to allow everything that is allowed on r.h.s. of a normal assignment.

New changeset 62c35a8a8ff5854ed470b1c16a7a14f3bb80368c by Ivan Levkivskyi in branch 'master':
bpo-35814: Allow same r.h.s. in annotated assignments as in normal ones (GH-11667)
https://github.com/python/cpython/commit/62c35a8a8ff5854ed470b1c16a7a14f3bb80368c

I think PEP 526 does not clarify the intention here. Perhaps we could add a specific example? It currently shows:

  t: Tuple[int, ...] = (1, 2, 3)

We could just add this there:

  t: Tuple[int, ...] = 1, 2, 3

(With a comment indicating that the second is only accepted in Python 3.8 and later.)

Is PEP the best place for such updates? Maybe we can add a `versionchanged` note in https://docs.python.org/3/reference/simple_stmts.html#annotated-assignment-statements instead?

> Is PEP the best place for such updates? Maybe we can add a `versionchanged` note in https://docs.python.org/3/reference/simple_stmts.html#annotated-assignment-statements instead?

We should definitely update the docs, with `versionchanged`.

But we should also update the PEP, because the reason this was changed was an interpretation issue in the PEP.  This is different from simply changing things in a later version because we've come up with a new idea or we've learned that something was a bad idea.

Now that the intention of the PEP has been clarified, the PEP itself ought to be updated with words expressing the clearer version; but because previously the intended syntax wasn't supported, it makes sense to also add a note there that this wasn't implemented correctly until 3.8.

New changeset 8565f6b6db0fa9f65449b532a5056a98bad3dc37 by Pablo Galindo in branch 'master':
bpo-35814: Allow unpacking in r.h.s of annotated assignment expressions (GH-13760)
https://github.com/python/cpython/commit/8565f6b6db0fa9f65449b532a5056a98bad3dc37