Hi Guix,

I'm using Guix from commit 68b22a85419a52dcdb47422c10f9575b5d332790. When 
I try to run `guix deploy` using the attatched configuration, I receive 
the following error:

```
$ guix deploy -v3 config.scm
The following 1 machine will be deployed:
   kiosk

guix deploy: deploying to kiosk...
guix deploy: sending 0 store items (0 MiB) to 'kiosk.jackhill.us'...
guix deploy: sending 0 store items (0 MiB) to 'kiosk.jackhill.us'...
guix deploy: sending 0 store items (0 MiB) to 'kiosk.jackhill.us'...
guix deploy: sending 2 store items (0 MiB) to 'kiosk.jackhill.us'...
guix deploy: error: program `/gnu/store/3lig4b2i1qaisg9yx8nbl0xp8hgh40a7-guix-1.0.1-15.0984481/bin/guix' failed with exit code 1
```

The error would appear to occur when creating the grub configuration, 
because both /run/current-system and the list reported by `guix system 
list-generations` show the newly created generation, but it is not present 
in the grub configuration.

The last time I sucessfully used guix deploy on this host was with Guix 
830dab870ab1d4a4ec1127a877a43d19f86c4f7f on March 20th, 2020 (yes, the 
pandemic has kept me away from working on this host for some time).

Best,
Jack