bug#33107: guix pull error

[Marcel Schilling]

addendum: a 2nd guix pull finished successfully:

> Generation 6    Oct 20 2018 21:43:33    (current)
>   guix bfa47f1
>     repository URL: https://git.savannah.gnu.org/git/guix.git
>     branch: master
>     commit: bfa47f14b1a19150d6ddf149597d16493f69ae6d