Python version 3.10.0a7 added a more informative error message for:

>>> f"{**k}"
  File "<stdin>", line 1
    (**k)
     ^
SyntaxError: f-string: can't use double starred expression here

Previously, the message was simply "SyntaxError: invalid syntax".  So, this change is certainly a welcome addition.

However, as far as I can tell, starting with Python 3.8, all previous uses of "can't" in error messages were replaced by "cannot".  Although it is an extremely minor point, it might be preferable for consistency to replace "can't" by "cannot" in this new error message.