bug#52347: Shell: error when -m manifest is removed

[Cayetano Santos]

> mar. 07 déc. 2021 at 12:02, Maxime Devos <maximedevos@telenet.be> 
> ...

> What's the error message?

Output to ’guix shell --container -- python3’ gives

guix shell: avertissement : aucun paquet spécifié ; création d'un 
environnement vide
guix shell: erreur : python3: command not found
Backtrace:
         16 (primitive-load "/usr/local/bin/guix")
In guix/ui.scm:
  2206:7 15 (run-guix . _)
 2169:10 14 (run-guix-command _ . _)
In ice-9/boot-9.scm:
 1752:10 13 (with-exception-handler _ _ #:unwind? _ # _)
 1752:10 12 (with-exception-handler _ _ #:unwind? _ # _)
In guix/store.scm:
  658:37 11 (thunk)
  1320:8 10 (call-with-build-handler _ _)
  1320:8  9 (call-with-build-handler #<procedure 7fbb1d6516f0 at 
  g…> …)
In guix/status.scm:
   800:4  8 (call-with-status-report _ _)
In guix/scripts/environment.scm:
  951:12  7 (_)
In guix/store.scm:
 2119:24  6 (run-with-store #<store-connection 256.99 
 7fbb2132ccd0> …)
In guix/scripts/environment.scm:
  627:17  5 (_ _)
  576:23  4 (validate-exit-status _ _ 32512)
In guix/utils.scm:
   954:4  3 (string-closest _ _ #:threshold _)
In guix/combinators.scm:
   46:32  2 (fold2 #<procedure 7fbb10e14380 at 
   guix/utils.scm:954:…> …)
In ice-9/boot-9.scm:
 1685:16  1 (raise-exception _ #:continuable? _)
 1685:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1685:16: In procedure raise-exception:
In procedure car: Wrong type argument in position 1 (expecting 
pair): #f