Hi Artyom, 

"Artyom V. Poptsov" <poptsov.artyom@gmail.com> writes:

> Initialized empty Git repository in /gnu/store/dpbxqzqmbhfy7jc2a9dyfi28fdvi04sd-guile-gnutls-3.7.11-checkout/.git/
> fatal: unable to access 'https://gitlab.com/gnutls/guile/': The requested URL returned error: 403
> Failed to do a shallow fetch; retrying a full fetch...
> fatal: unable to access 'https://gitlab.com/gnutls/guile/': The requested URL returned error: 403
> git-fetch: 'git fetch origin' failed with exit code 128

It rather seems like you're just getting a 403 from gitlab, not that
you can't validate the TLS certificate.  Can you access that url from a
browser?  Are you using a proxy, but the Guix daemon is somehow not
using it?

Best,
-- 
Josselin Poiret