def build_tracker_url(portal_url=None):
    """
        Creates a url that can be used to open Tracker for ArcGIS

        ==================     ====================================================================
        **Argument**           **Description**
        ------------------     --------------------------------------------------------------------
        portal_url             Optional :class:`String` The portal that should be used when tracker
                               is launched via the url scheme.
        ==================     ====================================================================

        :return: :class:`String`
    """
    url = "arcgis-tracker://"
    if portal_url is not None:
        url += "?portalURL={}".format(portal_url)
    return url