'Delete the item (item_name, item_category) from the User category with
key user_cat. Any leading \'@\' characters are removed'

def do_del_item_from_user_cat(self, user_cat, item_name, item_category):

    if user_cat.startswith(u'@'):
        user_cat = user_cat[1:]
    db = self.library_view.model().db
    user_cats = db.prefs.get(u'user_categories', {})
    if (user_cat not in user_cats):
        error_dialog(self.tags_view, _(u'Remove    category'), (_(u'User    category    %s    does    not    exist') % user_cat), show=True)
        return
    self.tags_view.model().delete_item_from_user_category(user_cat, item_name, item_category)
    self.tags_view.recount()
    self.user_categories_edited()
