Comment 3 for bug 1633276

Verified from the command line:

fgimenez@fgimenez-Standard-PC-i440FX-PIIX-1996:~$ for value in yes no 0 1 unicorn; do
> SNAP_CONFINE_DEBUG=$value ubuntu-core-launcher blah 2>debug.$value || :
> done
fgimenez@fgimenez-Standard-PC-i440FX-PIIX-1996:~$ cat debug.yes
DEBUG: shifting arguments by one
Usage: ubuntu-core-launcher <security-tag> <binary>
fgimenez@fgimenez-Standard-PC-i440FX-PIIX-1996:~$ cat debug.1
DEBUG: shifting arguments by one
Usage: ubuntu-core-launcher <security-tag> <binary>
fgimenez@fgimenez-Standard-PC-i440FX-PIIX-1996:~$ cat debug.no
Usage: ubuntu-core-launcher <security-tag> <binary>
fgimenez@fgimenez-Standard-PC-i440FX-PIIX-1996:~$ cat debug.0
Usage: ubuntu-core-launcher <security-tag> <binary>
fgimenez@fgimenez-Standard-PC-i440FX-PIIX-1996:~$ cat debug.unicorn
WARNING: unrecognized value of environment variable SNAP_CONFINE_DEBUG (expected yes/no or 1/0)
Usage: ubuntu-core-launcher <security-tag> <binary>. errmsg: Invalid argument