bug#46942: ci.guix.gnu.org is slow from my system

[raid5atemyhomework]

Hi Maxime,

> On Mon, 2021-03-15 at 00:13 +0000, raid5atemyhomework via Bug reports for GNU 
> Guix wrote:
>
> > Hello all,
> > [...]
> > I recently had to rebuild an OS (because I was dumb; the Guix language
> > for shepherd services can easily lead you deadlocking shepherd itself)
> > and had supreme difficulty reinstalling, [...]
>
> Reinstalling after a messed up configuration file shouldn't be necessary.
> At least when using GRUB as bootloader, guix keeps some old (& presumably
> not broken) system generations around, that can be selected when booting
> from the bootloader. (I don't recall exactly how the menu is named,
> maybe ‘Old system generations of $HOSTNAMES?)

Unfortunately I had a long-standing latent bug in my configuration file that 
triggered on a (persistent on-disk) edge case which would cause the shepherd 
process to enter an infinite loop (because the shepherd configuration language 
is Turing-complete enough to allow infinite loops in the first place).  All the 
remaining generations (since I didn't like keeping more than a dozen, and had 
recently been excessively tweaking the configuration file) had this bug, so I 
had no way of reverting to an even older generation that predated the bug.

Thanks
raid5atemyhomework