Callback for partial output.

def _partial(self):
        """Callback for partial output."""
        raw_stdout = self._process.readAllStandardOutput()
        stdout = handle_qbytearray(raw_stdout, _CondaAPI.UTF8)

        json_stdout = stdout.replace('\n\x00', '')
        try:
            json_stdout = json.loads(json_stdout)
        except Exception:
            json_stdout = stdout

        if self._partial_stdout is None:
            self._partial_stdout = stdout
        else:
            self._partial_stdout += stdout

        self.sig_partial.emit(self, json_stdout, None)