Move env fix from caller to callee.

This way tails-additional-software-notify will open a browser with
propoer "GNOME" environment no matter who calls it.

config/chroot_local-includes/usr/local/lib/tails-additional-software-notify

@@ -6,6 +6,8 @@ import os.path
 import subprocess
 import sys
 
+from tailslib.gnome import gnome_env_vars
+
 import gi
 
 from gi.repository import GLib
@@ -56,7 +58,9 @@ class ASPNotifier(object):
         elif action == "deny":
             sys.exit(3)
         elif action == "documentation":
-            subprocess.Popen(["tails-documentation", user_data])
+            subprocess.Popen(
+                ["env", *gnome_env_vars(), "tails-documentation", user_data]
+            )
             sys.exit(5)
 
     def cb_notification_closed(self, notification):

config/chroot_local-includes/usr/local/sbin/tails-additional-software

@@ -23,8 +23,6 @@ from tailslib.additionalsoftware import (
     get_packages_list_path,
     remove_additional_packages)
 
-from tailslib.gnome import gnome_env_vars
-
 from tailslib.persistence import (
     has_unlocked_persistence,
     has_persistence,
@@ -112,7 +110,6 @@ def _notify(title, body="", accept_label="", deny_label="",
         completed_process = subprocess.run(
             [
                 "sudo", "-u", LIVE_USERNAME,
-                'env', *gnome_env_vars(),
                 cmd, title, body, accept_label, deny_label,
                 documentation_target, urgent
             ],