[gnome-shell-extensions] drive-menu: Add a translator comment explaining a variable

[Piotr Drąg <piotrdrag src gnome org>]

commit 71ba8b04d79545777ddc00ed574f775a0a61a265
Author: Piotr Drąg <piotrdrag gmail com>
Date:   Wed Aug 2 17:11:28 2017 +0200

    drive-menu: Add a translator comment explaining a variable
    
    https://bugzilla.gnome.org/show_bug.cgi?id=687590

 extensions/drive-menu/extension.js |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/extensions/drive-menu/extension.js b/extensions/drive-menu/extension.js
index bda866c..f0b1068 100644
--- a/extensions/drive-menu/extension.js
+++ b/extensions/drive-menu/extension.js
@@ -103,6 +103,7 @@ const MountMenuItem = new Lang.Class({
     },
 
     _reportFailure: function(exception) {
+       // TRANSLATORS: %s is the filesystem name
        let msg = _("Ejecting drive “%s” failed:").format(this.mount.get_name());
        Main.notifyError(msg, exception.message);
     },