bug#40899: Locales not set up correctly

[Matthew Kraai]

Hi,

After I launch an EC2 instance using the official Debian 10 Buster AMI
and run the attached script, which should match the installation
instructions in the manual, the locales don't seem to be set up
properly.  For example,

```
$ guix package -i nss-certs
guile: warning: failed to install locale
hint: Consider installing the `glibc-utf8-locales' or `glibc-locales' package 
and
defining `GUIX_LOCPATH', along these lines:

     guix package -i glibc-utf8-locales
     export GUIX_LOCPATH="$HOME/.guix-profile/lib/locale"

See the "Application Setup" section in the manual, for more info.

guix package: warning: Consider running 'guix pull' followed by
'guix package -u' to get up-to-date packages and security updates.

The following package will be installed:
   nss-certs 3.50

substitute: 
/gnu/store/29jhbbg1hf557x8j53f9sxd9imlmf02a-bash-minimal-5.0.7/bin/bash: 
warning: setlocale: LC_ALL: cannot change locale (en_US.utf8)
0.1 MB will be downloaded:
   /gnu/store/0y63pfqi2626nwsjbksrci1jyd62cxx8-nss-certs-3.50
/gnu/store/29jhbbg1hf557x8j53f9sxd9imlmf02a-bash-minimal-5.0.7/bin/bash: 
warning: setlocale: LC_ALL: cannot change locale (en_US.utf8)
downloading from 
https://ci.guix.gnu.org/nar/lzip/0y63pfqi2626nwsjbksrci1jyd62cxx8-nss-certs-3.50...
 nss-certs-3.50  133KiB               189KiB/s 00:00 [########          ]  
48.3%Backtrace:
In ice-9/boot-9.scm:
  1736:10  4 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
           3 (apply-smob/0 #<thunk 7f6763f15400>)
In ice-9/boot-9.scm:
    718:2  2 (call-with-prompt _ _ #<procedure default-prompt-handle?>)
In ice-9/eval.scm:
    619:8  1 (_ #(#(#<directory (guile-user) 7f6763b17f00>)))
In guix/ui.scm:
  1936:12  0 (run-guix-command _ . _)

guix/ui.scm:1936:12: In procedure run-guix-command:
Throw to key `encoding-error' with args `("scm_to_stringn" "cannot convert wide 
string to output locale" 84 #f #f)'.
substitution of /gnu/store/0y63pfqi2626nwsjbksrci1jyd62cxx8-nss-certs-3.50 
failed
guix package: error: some substitutes for the outputs of derivation 
`/gnu/store/mxp55201zl6wm2d82xdjnc8qa7qwgr85-nss-certs-3.50.drv' failed 
(usually happens due to networking issues); try `--fallback' to build 
derivation from source 
```

-- 
Matthew Kraai

install_guix.sh
Description: Bourne shell script