'Returns a tuple (data, present).
\'present\' is whether the data was found in self.bind_to
\'data\' is the data itself, or None whenever present is False'

def _get_data_and_presence(self):

    try:
        if (self.grab_key is not _ANONYMOUS):
            present = (self.grab_key in self.bind_to)
            data = self.bind_to.get(self.grab_key)
        else:
            present = True
            data = self.bind_to
    except AttributeError:
        LOG.exception(("Error    value    of    key    '%s'    in    configuration." % self.grab_key))
        data = _('Possible    misconfiguration')
        present = True
    return (data, present)
