bug#35883: guix import hackage: recursive import fails silently on errors

[Robert Vollmert]

$ guix import hackage not-a-package
guix import: error: failed to download cabal file for package 'not-a-package’
$ echo $?
1
$ guix import hackage -r not-a-package
$ echo $?
0

It might be argued that the error code is fine, since in general it could be
useful for the recursive import to keep going past failures. However it seems
such failures should be logged, and ideally written to standard output in some
form like

(error “import failed: <package name>”)

so they could be found clearly in the generated expression.