Gnome-tweaks does not look at GSETTINGS_SCHEMA_PATH or XDG_DATA_DIRS, it
assumes that schemas are installed in one global directory
(GSETTINGS_SCHEMA_DIR/gsettingsschemadir).

Guix/GuixSD uses a different directory for every gir package and has
packages pick-up files using XDG_DATA_DIRS.

Upstream ticket: https://bugzilla.gnome.org/show_bug.cgi?id=764537
janneke@gnu.org

--- gnome-tweak-3.18.1.orig/gtweak/gsettings.py	2015-04-08 15:21:32.000000000 +0200
+++ gnome-tweak-tool-3.18.1/gtweak/gsettings.py	2016-04-03 11:26:38.658482704 +0200
@@ -16,7 +16,8 @@
 # along with gnome-tweak-tool.  If not, see <http://www.gnu.org/licenses/>.
 
 import logging
-import os.path
+import os
+import sys
 import xml.dom.minidom
 import gettext
 
@@ -31,6 +32,13 @@
 class GSettingsMissingError(Exception):
     pass
 
+def file_from_path(path, file_name):
+    for dir in path:
+        f = os.path.join(dir, file_name)
+        if os.path.exists(f):
+            return f
+    return None
+
 class _GSettingsSchema:
     def __init__(self, schema_name, schema_dir=None, schema_filename=None, **options):
         if not schema_dir:
@@ -38,9 +46,14 @@
         if not schema_filename:
             schema_filename = schema_name + ".gschema.xml"
 
+        schema_prefix = os.path.join('glib-2.0', 'schemas')
         schema_path = os.path.join(schema_dir, schema_filename)
         if not os.path.exists(schema_path):
-            logging.critical("Could not find schema %s" % schema_path)
+            schema_path = file_from_path(os.environ.get ('GSETTINGS_SCHEMA_PATH', '').split(os.path.pathsep), schema_filename)
+        if not (schema_path and os.path.exists(schema_path)):
+            schema_path = file_from_path(os.environ.get ('XDG_DATA_DIRS', '').split(os.path.pathsep), os.path.join(schema_prefix, schema_filename))
+        if not (schema_path and os.path.exists(schema_path)):
+            logging.critical("Could not find schema %s" % schema_filename)
             assert(False)
 
         self._schema_name = schema_name
8fbac0e020fbfe92a6bf880065ac'>root</a>/<a href='/guix/log/tests?id=0f89d91411f68fbac0e020fbfe92a6bf880065ac'>tests</a>/<a href='/guix/log/tests/texlive.scm?id=0f89d91411f68fbac0e020fbfe92a6bf880065ac'>texlive.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/texlive.scm?id=0f89d91411f68fbac0e020fbfe92a6bf880065ac&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-07-22 23:03:46 +0200'>2022-07-22</span></td><td><a href='/guix/commit/tests/texlive.scm?id=c9a37f57cbb18be01436a709cbdd96ffea41caf5'>tests: Adjust texlive importer tests.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2022-01-13 23:11:19 +0100'>2022-01-13</span></td><td><a href='/guix/commit/tests/texlive.scm?id=641b599d0bd1902abeab19e286cdd6c368f8daa3'>import: texlive: Remove labels from 'propagated-inputs' field.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-01-11 20:26:39 +0100'>2022-01-11</span></td><td><a href='/guix/commit/tests/texlive.scm?id=10b2ad7dbf01eda67685ace03ff2e0c8afc7a309'>tests: Fix texlive test by sorting locations.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2021-11-18 13:17:57 +0000'>2021-11-18</span></td><td><a href='/guix/commit/tests/texlive.scm?id=f66da037b457f5d92a0b3e3f53121e17571b42c4'>tests: Replace texlive importer tests.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2021-03-06 11:41:48 +0100'>2021-03-06</span></td><td><a href='/guix/commit/tests/texlive.scm?id=c05ceaf2b650d090cf39a048193505cb4e6bd257'>tests: do not hard code HTTP ports</a><span class='msg-avail'>...</span></td><td>Maxime Devos</td></tr>
<tr><td><span title='2020-01-17 14:22:08 +0100'>2020-01-17</span></td><td><a href='/guix/commit/tests/texlive.scm?id=6f918d69b4824226c877c0ca6385360a1dd38bbd'>import: texlive: Avoid uses of '@@' in tests.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>