discovery: Remove dependency on (guix ui).

This reduces the closure of (guix discovery) from 28 to 8 modules.

* guix/discovery.scm (scheme-files): Use 'format' instead of 'warning'.
(scheme-modules): Add #:warn parameter.  Use it instead of
'warn-about-load-error'.
(fold-modules): Add #:warn and pass it to 'scheme-modules'.
(all-modules): Likewise.
* gnu/bootloader.scm (bootloader-modules): Pass #:warn to 'all-modules'.
* gnu/packages.scm (fold-packages): Likewise.
* gnu/services.scm (all-service-modules): Likewise.
* guix/upstream.scm (importer-modules): Likewise.

1 files changed, 4 insertions, 2 deletions

diff --git a/gnu/packages.scm b/gnu/packages.scm
index 44a56dfde0..1a37a17342 100644
--- a/gnu/packages.scm
+++ b/gnu/packages.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
 ;;; Copyright © 2016, 2017 Alex Kost <alezost@gmail.com>
@@ -159,7 +159,9 @@ for system '~a'")
 
 (define* (fold-packages proc init
                         #:optional
-                        (modules (all-modules (%package-module-path)))
+                        (modules (all-modules (%package-module-path)
+                                              #:warn
+                                              warn-about-load-error))
                         #:key (select? (negate hidden-package?)))
   "Call (PROC PACKAGE RESULT) for each available package defined in one of
 MODULES that matches SELECT?, using INIT as the initial value of RESULT.  It