Remove invalid characters from the label name

db/migrate/20140729152420_migrate_taggable_labels.rb

@@ -15,7 +15,7 @@ class MigrateTaggableLabels < ActiveRecord::Migration
 
   def create_label_from_tagging(tagging)
     target = tagging.taggable
-    label_name = tagging.tag.name
+    label_name = tagging.tag.name.tr('?&,', '')
     label = target.project.labels.find_or_create_by(title: label_name)
 
     if label.valid? && LabelLink.create(label: label, target: target)