getnonfreefonts: tug.org certificate errors

[Karl Berry]

     | Resolving www.tug.org... 94.23.251.76
     | Connecting to www.tug.org|94.23.251.76|:443... connected.
     | ERROR: The certificate of 'www.tug.org' is not trusted.
     | ERROR: The certificate of 'www.tug.org' has expired.
     | ! Error: Can't execute wget.

To the best of my knowledge, the certificates on the user's machine have
to be updated. It's a network-wide issue, not related to tug.org or
getnonfreefonts.

Here is a brief description and some further references:
https://savannah.nongnu.org/forum/forum.php?forum_id=10054