I may be mistaken, but I do not think the change introduced a regression.

While it is true that this case would not have appeared if there was
still a count of the field-separators an IPv6 address with 5 ':' and 17
characters would have failed as well. The value being examined is based
on it's position, and previously the additional assumption is that
whatever is in that position is a MACADDR if it uses the system
separator ('.' on AIX, ':' elsewhere).

If anyone is interested I will think about what are assumptions are - is
this a value we should be considering, or not.

IMHO - while issue39991 is resolved - I am not -yet- convinced that the
"root cause" has been identified and properly coded

Michael

On 17/03/2020 16:14, STINNER Victor wrote:
> STINNER Victor <vstinner@python.org> added the comment:
>
>> New changeset 0bcbfa43d55d9558cdcb256d8998366281322080 by Tal Einat (Michael Felt) in branch 'master':
>> bpo-28009: Fix uuid.uuid1() and uuid.get_node() on AIX (GH-8672)
> This change introduced a regression: bpo-39991.
>
> I pushed the commit eb886db1e99a15f15a2342aa496197a5f88fa9c8 to fix my case, but I'm not sure that the fix covers all cases.
>
> ----------
> nosy: +vstinner
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <https://bugs.python.org/issue28009>
> _______________________________________
>