def _add_cmd_output(self, cmd, suggest_filename=None,
                        root_symlink=None, timeout=300, stderr=True,
                        chroot=True, runat=None, env=None, binary=False,
                        sizelimit=None, pred=None):
        """Internal helper to add a single command to the collection list."""
        cmdt = (
            cmd, suggest_filename,
            root_symlink, timeout, stderr,
            chroot, runat, env, binary, sizelimit
        )
        _tuplefmt = ("('%s', '%s', '%s', %s, '%s', '%s', '%s', '%s', '%s', "
                     "'%s')")
        _logstr = "packed command tuple: " + _tuplefmt
        self._log_debug(_logstr % cmdt)
        if self.test_predicate(cmd=True, pred=pred):
            self.collect_cmds.append(cmdt)
            self._log_info("added cmd output '%s'" % cmd)
        else:
            self._log_info("skipped cmd output '%s' due to predicate (%s)" %
                           (cmd, self.get_predicate(cmd=True, pred=pred)))
Internal helper to add a single command to the collection list.