$ guix describe
Generation 98   21. Juni 2019 18:33:36  (aktuell)
  guix e6049c8
    Repository-URL: https://git.savannah.gnu.org/git/guix.git
    Branch: master
    Commit: e6049c84dab3031fb64defae2c45a20b512d4644

GUIX_PACKAGE_PATH=""
$ guix environment -s i686-linux --ad-hoc gcc-toolchain@5.5.0
The following derivation will be built:
   /gnu/store/2f7lzsp1i70rxb9yzfwr69amlmyy0r60-profile.drv
0.0 MB will be downloaded:
   /gnu/store/hwyhdah35bv4xkqg4rdaw7a1hs5ny3mk-gcc-toolchain-5.5.0
The following profile hook will be built:
   /gnu/store/sqv5pp0pjjzrnzshgyn365sf413pl1bp-manual-database.drv
following redirection to `https://ci.guix.gnu.org'...
Backtrace:
           3 (apply-smob/1 #<catch-closure 1d1f640>)
In ice-9/boot-9.scm:
    705:2  2 (call-with-prompt _ _ #<procedure default-prompt-handle?>)
In ice-9/eval.scm:
    619:8  1 (_ #(#(#<directory (guile-user) 1da2140>)))
In guix/ui.scm:
  1734:12  0 (run-guix-command _ . _)

guix/ui.scm:1734:12: In procedure run-guix-command:
In procedure put-string: Wrong type argument in position 1 (expecting open output port): #<closed: string 2322cb0>
substitution of /gnu/store/hwyhdah35bv4xkqg4rdaw7a1hs5ny3mk-gcc-toolchain-5.5.0 failed
building database for manual pages...
guix environment: error: some substitutes for the outputs of derivation `/gnu/store/zxxw95x9ivw1a10v6nk1ls6d9i1csh3y-gcc-toolchain-5.5.0.drv' failed (usually happens due to networking issues); try `--fallback' to build derivation from source