Embedded Python3 raise an exception when importing a local module

I’m trying to embed a Pyhton3 program into a C++ one. After following several tutorials and blog posts I get the following code, which fails:

Py_SetProgramName(_program_name);
Py_Initialize();

PyObject* main = PyImport_AddModule("__main__");
PyObject* globalDictionary = PyModule_GetDict(main);
PyObject* localDictionary = PyDict_New();
//create the dictionaries as shown above
PyObject* pythonpath = PySys_GetObject("path");
if (PyList_Append(pythonpath, PyBytes_FromString("/path/to/my/modules")) ==  -1)
{
  std::cerr << "Failed to append to python path" << std::endl;
  PyErr_Print();
}
const char* pythonScript = ""
"import sysn"
"print('Hello')n"
"import optionsn"
"print('World')n"
"";
PyObject* returnValue = PyRun_String(pythonScript, Py_file_input, globalDictionary, localDictionary);
if (!returnValue)
{
  std::cerr << "python raised an exception" << std::endl;
  PyErr_Print();
  return 1;
}

The result is the following:

Hello
python raised an exception
Traceback (most recent call last):
  File "<string>", line 5, in <module>
  File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
  File "<frozen importlib._bootstrap>", line 2222, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 2164, in _find_spec
  File "<frozen importlib._bootstrap>", line 1940, in find_spec
  File "<frozen importlib._bootstrap>", line 1914, in _get_spec
  File "<frozen importlib._bootstrap>", line 2049, in find_spec
  File "<frozen importlib._bootstrap>", line 53, in _path_join
  File "<frozen importlib._bootstrap>", line 53, in <listcomp>
TypeError: 'str' does not support the buffer interface

So, importing sys works but importing my own module fails, while adding the path to my modules seemed to work.

Any idea ?

Answer

Replacing PyBytes_FromString by PyUnicode_DecodeFSDefault made the import work. I don’t understand why though.