def validate_bug_tracker_base_hosting_url(input_url):
    # Try formatting the URL using an empty tuple to verify that it
    # doesn't contain any format characters.
    try:
        input_url % ()
    except TypeError:
        raise ValidationError([
            _("The URL '%s' is not valid because it contains a format "
              "character. For bug trackers other than 'Custom Bug Tracker', "
              "use the base URL of the server. If you need a '%%' character, "
              "prepend it with an additional '%%'.") % input_url])
Check that hosting service bug URLs don't contain %s.
dataset/ETHPy150Open reviewboard/reviewboard/reviewboard/admin/validation.py/validate_bug_tracker_base_hosting_url