Consider the following in Python 3.10

>>> ... = 1
  File "<stdin>", line 1
    ... = 1
    ^^^
SyntaxError: cannot assign to Ellipsis here. Maybe you meant '==' instead of '='?
>>> __debug__ = 1
  File "<stdin>", line 1
SyntaxError: cannot assign to __debug__

In prior Python versions, assignments to Ellisis written as ... were treated the same as assignment to __debug__. I believe that the old message was a better choice.

The error message about assigning to Ellipsis (...) is made even more confusing since Ellipsis (the name) can be assigned to a different value.

>>> ... == Ellipsis
True
>>> Ellipsis = 1
>>> ... == Ellipsis
False
>>> ...
Ellipsis