The site uses this callback routine to establish the access
    modes and access hours available to the user. If the user is
    not authorized to access the system from this login class (batch,
    dialup, local, remote, network) at this time (as specified in the
    UAF), the callback routine:

    o  Writes its standard error message to the user terminal, if
       there is a terminal

    o  Does not return control to the caller