Py_SetPythonHome is deprecated

[SylvainCorlay]

We are seeing the following error message in CI:

/src/xpaths.cpp:75:60: warning: 'void Py_SetPythonHome(const wchar_t*)' is deprecated [-Wdeprecated-declarations]
   75 |         Py_SetPythonHome(const_cast<wchar_t*>(wstr.c_str()));