When an equal sign is used instead of a colon in creating a dict literal, depending on the context, either the "bad token" is misidentified OR the would-be helpful error message is incorrect in this particular case.

1) Example of bad token.
Previously, the = sign was identified correctly:

>>> ages = {'Alice'=22, 'Bob'=23}
  File "<stdin>", line 1
    ages = {'Alice'=22, 'Bob'=23}
                   ^
SyntaxError: invalid syntax

With Python 3.10.0b1, the comma is identified as the bad token:

>>> ages = {'Alice'=22, 'Bob'=23}
  File "<stdin>", line 1
    ages = {'Alice'=22, 'Bob'=23}
                      ^
SyntaxError: invalid syntax


2) Example of incorrect error message

Previously, we got the traditional and unhelpful "invalid syntax" but with the bad token identified correctly:

>>> ages = {'Alice'=22}
  File "<stdin>", line 1
    ages = {'Alice'=22}
                   ^
SyntaxError: invalid syntax

With Python 3.10.0b1, we get the following:

>>> ages = {'Alice'=22}
  File "<stdin>", line 1
    ages = {'Alice'=22}
            ^^^^^^^
SyntaxError: cannot assign to literal here. Maybe you meant '==' instead of '='?

I suspect that the ratio (== suggestion correct/ : suggestion correct) would be vanishingly small. ;-)