Often I'll get this output when building a manifest* with an inferior:
```
itsme@antelope /tmp$ guix package -n -m example-inferior.scm
Updating channel 'guix' from Git repository at
'https://git.savannah.gnu.org/git/guix.git'...
guix package: error: failed to load 'example-inferior.scm':
```
I believe this is the 'inferior-for-channels' function that fails.
After investigating a while back, it seems removing the relevant checkout in
~/.cache/guix/checkouts temporarily fixes it, but the issue often comes back.
* The manifest used is the example from the Guix manual in the section on
Inferiors, with the guix commit in the manifest replaced with my guix revision:
```
(use-modules (guix inferior) (guix channels)
(srfi srfi-1)) ;for 'first'
(define channels
;; This is the old revision from which we want to
;; extract guile-json.
(list (channel
(name 'guix)
(url "https://git.savannah.gnu.org/git/guix.git";)
(commit
"722ac64cd7dc1f09fb77e2ae780427fa13c03110"))))
(define inferior
;; An inferior representing the above revision.
(inferior-for-channels channels))
;; Now create a manifest with the current "guile" package
;; and the old "guile-json" package.
(packages->manifest
(list (first (lookup-inferior-packages inferior "guile-json"))
(specification->package "guile")))
```
