Traceback formatting issue: SyntaxError and ExceptionGroup

[sobolevn]

Bug report

When raising SyntaxError with ExceptionGroup the traceback formatting seems to be broken:

>>> e = SyntaxError("error", ("x.py", 23, None, "bad syntax"))
>>> raise ExceptionGroup('A', [e])
  + Exception Group Traceback (most recent call last):
  |   File "<stdin>", line 1, in <module>
  | ExceptionGroup: A (1 sub-exception)
  +-+---------------- 1 ----------------
    |   File "x.py", line 23
    bad syntax
    | SyntaxError: error
    +------------------------------------

Note that bad syntax is not properly prefixed by | and not indented properly.

Compare it with:

>>> raise e
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "x.py", line 23
    bad syntax
SyntaxError: error

I expect it to be:

  + Exception Group Traceback (most recent call last):
  |   File "<stdin>", line 1, in <module>
  | ExceptionGroup: A (1 sub-exception)
  +-+---------------- 1 ----------------
    |   File "x.py", line 23
    |     bad syntax
    | SyntaxError: error
    +------------------------------------

This causes some side-effects on my work in #104150
So, I've prepared a PR to fix it. Polishing it and send today / tomorrow.

CC @iritkatriel

[sobolevn]

It is fixed on main, but not on 3.11.5.
This is the second time today I run a different python version 😒