RETURN instruction can be missing line number in except*

[markshannon]

Bug report

Bug description:

If the check in all_exits_have_lineno (flowgraph.c:520) is changed from instr->i_opcode == RETURN_VALUE to
instr->i_opcode == RETURN_VALUE || instr->i_opcode == RETURN_CONST then test_sys_settrace will fail with an assert.

The function triggering the assert is this:

def func():
    try:
        try:
            raise ValueError(3)
        except* TypeError:
            5
    except ValueError:
        7

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

[markshannon]

FYI, I'm planning on removing RETURN_CONST, which is how I discovered this. #125837

[iritkatriel]

If this is blocking you, feel free to comment out the assertion and leave a comment pointing to this issue.