def __init__(self, option, section, rawval, reference):
        msg = ("Bad value substitution:\n"
               "\tsection: [%s]\n"
               "\toption : %s\n"
               "\tkey    : %s\n"
               "\trawval : %s\n"
               % (section, option, reference, rawval))
        InterpolationError.__init__(self, option, section, msg)
        self.reference = reference
        self.args = (option, section, rawval, reference)