upower: Work around the daemon getting stuck after a suspend

modules/services/hardware/upower.nix

@@ -50,6 +50,15 @@ with pkgs.lib;
         mkdir -m 0755 -p /var/lib/upower
       '';
 
+    # The upower daemon seems to get stuck after doing a suspend
+    # (i.e. subsequent suspend requests will say "Sleep has already
+    # been requested and is pending").  So as a workaround, restart
+    # the daemon.
+    powerManagement.resumeCommands =
+      ''
+        ${config.system.build.systemd}/bin/systemctl try-restart upower
+      '';
+
   };
 
 }