message: Fix build: PyUnicode_AsUTF8AndSize returns a const char* in Python 3.7
diff: @@ -87,7 +87,7 @@ TfLiteType TfLiteTypeFromPyArray(PyArrayObject* array) {
  bool FillStringBufferFromPyUnicode(PyObject* value,
  DynamicBuffer* dynamic_buffer) {
  Py_ssize_t len = -1;
  - char* buf = PyUnicode_AsUTF8AndSize(value, &len);
  + const char* buf = PyUnicode_AsUTF8AndSize(value, &len);
  if (buf == NULL) {
  PyErr_SetString(PyExc_ValueError, "PyUnicode_AsUTF8AndSize() failed.");
  return false;
  