various fixes

aircox/templatetags/aircox_admin.py

@@ -2,7 +2,7 @@ import json
 from django import template
 from django.contrib import admin
 from django.utils.safestring import mark_safe
-from django.utils.translation import gettext_lazy as _, gettext as __
+from django.utils.translation import gettext_lazy as _
 
 from aircox.serializers.admin import UserSettingsSerializer
 
@@ -47,17 +47,19 @@ def do_track_inline_data(context, formset, safe_string=False):
     return safe_string and mark_safe(source) or source
 
 
+track_inline_labels_ = {
+    'artist': _('Artist'), 'album': _('Album'), 'title': _('Title'),
+    'tags': _('Tags'), 'year': _('Year'),
+    'save_settings': _('Save Settings'),
+    'discard_changes': _('Discard changes'),
+    'columns': _('Columns'),
+    'add_track': _('Add a track'),
+    'remove_track': _('Remove'),
+    'timestamp': _('Timestamp'),
+}
+
+
 @register.simple_tag(name='track_inline_labels')
 def do_track_inline_labels():
     """ Return labels for columns in playlist editor as dict """
-    return json.dumps({
-        'artist': __('Artist'), 'album': __('Album'), 'title': __('Title'),
-        'tags': __('Tags'), 'year': __('Year'),
-        'save_settings': __('Save Settings'),
-        'discard_changes': __('Discard changes'),
-        'columns': __('Columns'),
-        'add_track': __('Add a track'),
-        'remove_track': __('Remove'),
-        'timestamp': __('Timestamp'),
-    })
-
+    return json.dumps({k: str(v) for k, v in track_inline_labels_.items()})