$ guix pull

Starting download of /tmp/guix-file.1w9fX0
From http://git.savannah.gnu.org/cgit/guix.git/snapshot/master.tar.gz...
 ….tar.gz                                    22KiB/s 08:26 | 11.1MiB transferred
substitute: warning: failed to install locale: Invalid argument
substitute: Backtrace:
substitute: In ice-9/boot-9.scm:
substitute:  160: 9 [catch #t #<catch-closure 1e16d60> ...]
substitute: In unknown file:
substitute:    ?: 8 [apply-smob/1 #<catch-closure 1e16d60>]
substitute: In ice-9/boot-9.scm:
substitute:   66: 7 [call-with-prompt prompt0 ...]
substitute: In ice-9/eval.scm:
substitute:  432: 6 [eval # #]
substitute: In ice-9/boot-9.scm:
substitute: 2404: 5 [save-module-excursion #<procedure 1e36900 at ice-9/boot-9.scm:4051:3 ()>]
substitute: 4056: 4 [#<procedure 1e36900 at ice-9/boot-9.scm:4051:3 ()>]
substitute: 1727: 3 [%start-stack load-stack ...]
substitute: 1732: 2 [#<procedure 1e4ab70 ()>]
substitute: In unknown file:
substitute:    ?: 1 [primitive-load "/gnu/store/gj2i5xs7nm80mwrb139pa8iqfccw08zz-guix-0.12.0/bin/.guix-real"]
substitute: In guix/ui.scm:
substitute: 1222: 0 [run-guix-command substitute "--query"]
substitute:
substitute: guix/ui.scm:1222:8: In procedure run-guix-command:
substitute: guix/ui.scm:1222:8: Bad Read-Header-Line header: #<eof>
substitute:
guix pull: error: build failed: substituter `substitute' died unexpectedly