Error updating gnurl

[Tanguy LE CARROUR]

As mentionned on GNUnet mailing list [1][], gnurl is affected by security 
issues.

[1]: https://lists.gnu.org/archive/html/gnunet-developers/2022-04/msg00021.html

It might not affect GNUnet, but I tried to update the package in Guix anyway, 
and…
I failed! ^_^'

```console
$ ./pre-inst-env guix refresh -u gnurl

Starting download of /tmp/guix-file.NqJa4t
>From https://ftpmirror.gnu.org/gnu/gnunet/gnurl-7.72.0.tar.gz...
following redirection to 
`https://mirrors.ocf.berkeley.edu/gnu/gnunet/gnurl-7.72.0.tar.gz'...
 …2.0.tar.gz  3.3MiB                  3.1MiB/s 00:01 [##################] 100.0%

Starting download of /tmp/guix-file.VXn0IS
>From https://ftpmirror.gnu.org/gnu/gnunet/gnurl-7.72.0.tar.gz.sig...
following redirection to 
`https://mirrors.ocf.berkeley.edu/gnu/gnunet/gnurl-7.72.0.tar.gz.sig'...
 …0.tar.gz.sig  833B                  654KiB/s 00:00 [##################] 100.0%
gpgv: Signature made Wed 16 Sep 2020 22:30:16 CEST
gpgv:                using RSA key 6115012DEA3026F62A98A556D6B570842F7E7F8D
gpgv: Can't check signature: No public key
Would you like to add this key to keyring 
'/home/tanguy/.config/guix/upstream/trustedkeys.kbx'?
yes
gpg: keyserver receive failed: No data
guix refresh: warning: missing public key 
6115012DEA3026F62A98A556D6B570842F7E7F8D for 
'mirror://gnu/gnunet/gnurl-7.72.0.tar.gz'
guix refresh: warning: gnurl: version 7.72.0 could not be downloaded and 
authenticated; not updating
```

Have I done something wrong?!

Regards,

-- 
Tanguy