Porting Py3.8/Py3.9:

Since Py3.3: 'Py_ssize_t PyUnicode_GetSize(PyObject*)' is deprecated [-Wdeprecated-declarations]
Since Py3.9: 'PyObject* PyEval_CallObjectWithKeywords(PyObject*, PyObject*, PyObject*)' is deprecated [-Wdeprecated-declarations]
Since Py3.9: 'void PyEval_InitThreads()' is deprecated [-Wdeprecated-declarations]

src/Base/Interpreter.cpp

@@ -549,7 +549,11 @@ const char* InterpreterSingleton::init(int argc,char *argv[])
                 "    exec(open(activate_this).read(), {'__file__':activate_this})\n"
             );
         }
+
+#if PY_VERSION_HEX < 0x03090000
         PyEval_InitThreads();
+#endif
+
 #if PY_MAJOR_VERSION >= 3
         size_t size = argc;
         wchar_t **_argv = new wchar_t*[size];
@@ -700,7 +704,11 @@ void InterpreterSingleton::runMethod(PyObject *pobject, const char *method,
         throw TypeError("InterpreterSingleton::RunMethod() wrong arguments");
     }
 
+#if PY_VERSION_HEX < 0x03090000
     presult = PyEval_CallObject(pmeth, pargs);   /* run interpreter */
+#else
+    presult = PyObject_CallObject(pmeth, pargs);   /* run interpreter */
+#endif
 
     Py_DECREF(pmeth);
     Py_DECREF(pargs);