How to safely convert std::runtime_error that contains non UTF8 words to Python RuntimeError after pybind v2.7

[TianciXiao]

I implement a pybind method, which will call another lib to do some things. But this lib may raise exceptions contains non UTF8 words like '0xff'. So when I catch that exception and try to raise my own std::runtime_error. This pybind method will raise 'UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position xxx: invalid start byte' when I call MyFunc from Python.

.def("MyFunc", []() {
  try {
    call_other_func();
  } catch (const std::exception &err) {
    raise std::runtime_error("Call MyFunc failed, err: " + std::string(err.what()));
  }
})

This situation only occurs with pybind after v2.7. I guess it may be relative to the change about py::str https://pybind11.readthedocs.io/en/stable/upgrade.html#v2-7

So is there a safe way to convert std::runtime_error that contains non UTF8 words to Python RuntimeError?