Hello!

I'm trying to update librsvg, which requires "rust".

However adding this simple diff:

--- a/gnu/packages/gnome.scm
+++ b/gnu/packages/gnome.scm
@@ -114,6 +114,7 @@
   #:use-module (gnu packages pulseaudio)
   #:use-module (gnu packages python)
   #:use-module (gnu packages rdesktop)
+  #:use-module (gnu packages rust)
   #:use-module (gnu packages scanner)
   #:use-module (gnu packages selinux)
   #:use-module (gnu packages slang)

Causes the module to compile (sometimes), but any Guix action results in
a backtrace similar to this:

--8<---------------cut here---------------start------------->8---
guix build: warning: failed to load '(nonfree packages audio)':
In procedure module-lookup: Unbound variable: gcc
guix build: warning: failed to load '(nonfree packages games)':
Unbound variable: devil
guix build: warning: failed to load '(gnu packages avr)':
In procedure module-lookup: Unbound variable: binutils
guix build: warning: failed to load '(gnu packages axoloti)':
In procedure module-lookup: Unbound variable: gcc-4.9
guix build: warning: failed to load '(gnu packages bioconductor)':
In procedure module-lookup: Unbound variable: perl-module-build
guix build: warning: failed to load '(gnu packages bootloaders)':
no binding `bc' in module (gnu packages algebra)
guix build: warning: failed to load '(gnu packages chemistry)':
In procedure module-lookup: Unbound variable: python2-numpy
guix build: warning: failed to load '(gnu packages commencement)':
In procedure module-lookup: Unbound variable: gnu-make
guix build: warning: failed to load '(gnu packages debug)':
In procedure module-lookup: Unbound variable: gnu-make
guix build: warning: failed to load '(gnu packages display-managers)':
In procedure module-lookup: Unbound variable: gpgme
guix build: warning: failed to load '(gnu packages games)':
In procedure module-lookup: Unbound variable: unzip
guix build: warning: failed to load '(gnu packages image-viewers)':
In procedure module-lookup: Unbound variable: curl
guix build: warning: failed to load '(gnu packages license)':
In procedure module-lookup: Unbound variable: perl
guix build: warning: failed to load '(gnu packages make-bootstrap)':
In procedure module-lookup: Unbound variable: coreutils
guix build: warning: failed to load '(gnu packages syndication)':
In procedure module-lookup: Unbound variable: curl
guix build: warning: failed to load '(gnu packages unrtf)':
In procedure module-lookup: Unbound variable: coreutils
guix build: error: librsvg: unknown package
--8<---------------cut here---------------end--------------->8---

Not sure how to track down the module cycle.  Ideas?