bug#18935: gexp->derivation test failure

[Mark H Weaver <mhw@netris.org>]

On my i686 standalone Guix system, using Guix v0.7-642-g3b50925 to build
its 'guix' package (0.7.14e84b2) fails, due to a failed test.  Here's
the relevant section from gexp.log:

--8<---------------cut here---------------start------------->8---
Test begin:
  test-name: "gexp->derivation"
  source-file: "tests/gexp.scm"
  source-line: 227
  source-form: (test-assert "gexp->derivation" (run-with-store %store (mlet* %store-monad ((file (text-file "foo" "Hello, world!")) (exp -> (gexp (begin (mkdir (ungexp output)) (chdir (ungexp output)) (symlink (string-append (ungexp %bootstrap-guile) "/bin/guile") "foo") (symlink (ungexp file) (ungexp output "2nd"))))) (drv (gexp->derivation "foo" exp)) (out -> (derivation->output-path drv)) (out2 -> (derivation->output-path drv "2nd")) (done (built-derivations (list drv))) (refs ((store-lift references) out)) (refs2 ((store-lift references) out2)) (guile (package-file %bootstrap-guile "bin/guile"))) (return (and (string=? (readlink (string-append out "/foo")) guile) (string=? (readlink out2) file) (equal? refs (list (dirname (dirname guile)))) (equal? refs2 (list file))))) #:guile-for-bui
 ld (%guile-for-build)))
Test end:
  result-kind: fail
  actual-value: #f
  actual-error: (srfi-34 #<condition &nix-protocol-error [message: "path `/tmp/nix-build-guix-0.7.14e84b2.drv-0/source/test-tmp/store/ry17r3hm48ckcchz9ls6yhd00alyiipx-foo' is not valid" status: 1] a587d68>)
--8<---------------cut here---------------end--------------->8---

The 'guix-daemon' used to do this failed build is also 0.7.14e84b2.

The 'guix' used to do this failed build was v0.7-642-g3b50925 plus one
local patch that adds
"--with-default-trust-store-file=/etc/ssl/certs/ca-certificates.crt" to
the GnuTLS configure flags.

      Mark