bug#32855: sshuttle /usr/bin/env

[Nam Nguyen]

sshuttle is a python program that uses /usr/bin/env at line 196 of:
/gnu/store/...-sshuttle-0.78.4/lib/python3.6/site-packages/sshuttle/client.py
['sudo', '-p', '[local sudo] Password: ', '/usr/bin/env',

Trying to run sshuttle on GuixSD results in:
$ sshuttle -r address@hidden 0/0 -x server.com
sudo: /usr/bin/env: command not found

Here is a potential fix that I recycled from sshoot's recipe. I tested it,
and it works.

$ diff ~/.config/guix/current/share/guile/site/2.2/gnu/packages/vpn.scm 
~/vpn.scm
349a350,357
>     (arguments
>      '(#:phases
>        (modify-phases %standard-phases
>          (add-after 'unpack 'patch-paths
>            (lambda _
>              (substitute* "sshuttle/client.py"
>                (("/usr/bin/env") (which "env")))
>              #t)))))

Cheers,
Nam