bug#65804: Bug report: "You found a bug"

["Lasse Schlör" <lasse.schloer@uni-tuebingen.de>]

Hello,

The command that ran into this bug was:
`guix shell --manifest=guix-psychopy-manifest.scm`

The contents of `guix-psychopy-manifest.scm` were as follows:
```
(use-modules (guix inferior) (guix channels)
             (srfi srfi-1))

(define channels
  (list (channel
         (name 'guix)
         (url "https://git.savannah.gnu.org/git/guix.git")
         (commit
          ;; Last commit with Python 3.8
          "f1eea19c9ae27e5d275b083bbf280e5b59e5e57a"))))

(define inferior
  (inferior-for-channels channels))

(packages->manifest
 (list (first (lookup-inferior-packages inferior "python"))
       (specification->package "git")))
```

The command fetched/downloaded a lot of packages without issues. Then, the following output happened:
[…]
```
fetching path `/gnu/store/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8'...
-guix substitute: warning: while fetching https://ci.guix.gnu.org/nar/gzip/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8: server is somewhat slow
guix substitute: warning: try `--no-substitutes' if the problem persists
guix substitute: warning: download from 'https://ci.guix.gnu.org/nar/gzip/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8' failed, trying next URL
-guix substitute: warning: while fetching https://ci.guix.gnu.org/nar/lzip/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8: server is somewhat slow
guix substitute: warning: try `--no-substitutes' if the problem persists
guix substitute: warning: download from 'https://ci.guix.gnu.org/nar/lzip/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8' failed: 504, "Gateway Time-out"
retrying download of '/gnu/store/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8' with other substitute URLs...
guix substitute: warning: download from 'https://ci.guix.gnu.org/nar/gzip/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8' failed, trying next URL
guix substitute: warning: download from 'https://ci.guix.gnu.org/nar/lzip/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8' failed: 504, "Gateway Time-out"
guix substitute: error: failed to find alternative substitute for '/gnu/store/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8'
fetching path `/gnu/store/rw5z0mmdlcwkdzvr94bgihwlnhzwyky4-bzip2-boot0-1.0.8' (empty status: '')
fetching path `/gnu/store/gcl0d5i1hfg4s0fv21dgaf7r5z3i16zd-coreutils-boot0-8.32'...
Backtrace:
          15 (primitive-load "/gnu/store/fnyqpbdxbm4ipwvq9vfmxpkphdlqjcg3-compute-guix-derivation")
In ice-9/eval.scm:
    155:9 14 (_ _)
    159:9 13 (_ #(#(#(#(#(#(#(#(#(#(#(#(#(#<directory (guile-user) 7f51587cfc?> ?) ?) ?) ?) ?) ?) ?) ?) ?) ?) ?) ?) ?))
In ./guix/store.scm:
  2049:24 12 (run-with-store #<store-connection 256.99 7f51530fae60> #<procedure 7f5147f4bbc0 at ./guix/self.scm:12?> ?)
\   1883:8 11 (_ #<store-connection 256.99 7f51530fae60>)
In ./guix/gexp.scm:
   258:18 10 (_ #<store-connection 256.99 7f51530fae60>)
   1123:2  9 (_ #<store-connection 256.99 7f51530fae60>)
    982:2  8 (_ #<store-connection 256.99 7f51530fae60>)
    843:4  7 (_ #<store-connection 256.99 7f51530fae60>)
In ./guix/store.scm:
  1931:12  6 (_ #<store-connection 256.99 7f51530fae60>)
   1358:5  5 (map/accumulate-builds #<store-connection 256.99 7f51530fae60> #<procedure 7f514d350d40 at ./guix/stor?> ?)
  1369:15  4 (_ #<store-connection 256.99 7f51530fae60> ("/gnu/store/jwi2rqsz16lipgfl1h3084z8hiincnwv-guile-git-?" ?) ?)
  1369:15  3 (loop #f)
   715:11  2 (process-stderr #<store-connection 256.99 7f51530fae60> _)
In ./guix/serialization.scm:
   101:11  1 (read-int #<input-output: file 10>)
     79:6  0 (get-bytevector-n* #<input-output: file 10> 8)

./guix/serialization.scm:79:6: In procedure get-bytevector-n*:
ERROR:
  1. &nar-error:
      file: #f
      port: #<input-output: file 10>
guix shell: error: You found a bug: the program '/gnu/store/fnyqpbdxbm4ipwvq9vfmxpkphdlqjcg3-compute-guix-derivation'
failed to compute the derivation for Guix (version: "f1eea19c9ae27e5d275b083bbf280e5b59e5e57a"; system: "x86_64-linux";
host version: "6113e0529d61df7425f64e30a6bf77f7cfdfe5a5"; pull-version: 1).
Please report it by email to <bug-guix@gnu.org>.
```

As requested by Guix, I am reporting the bug with this email.

I assume this bug happened upon a temporary loss of the internet connection. Running the command anew continued fetching/downloading just fine.

Kind regards
Lasse Schlör