Remove PyEval methods deprecated in Python 3.9

Utilities/PythonInterpreter/vtkPythonInterpreter.cxx

@@ -248,11 +248,16 @@ bool vtkPythonInterpreter::Initialize(int initsigs /*=0*/)
     PySys_SetArgvEx(0, nullptr, 0);
 
 #ifdef VTK_PYTHON_FULL_THREADSAFE
+#if PY_VERSION_HEX < 0x03090000
+    // In Python 3.9 and higher, PyEval_ThreadsInitialized() and
+    // PyEval_InitThreads() are deprecated and do nothing.
+    // GIL initialization is handled by Py_InitializeEx().
     int threadInit = PyEval_ThreadsInitialized();
     if (!threadInit)
     {
       PyEval_InitThreads(); // initialize and acquire GIL
     }
+#endif
     // Always release GIL, as it has been acquired either by PyEval_InitThreads
     // prior to Python 3.7 or by Py_InitializeEx in Python 3.7 and after
     PyEval_SaveThread();

Wrapping/PythonCore/vtkPythonCommand.cxx

@@ -234,7 +234,7 @@ void vtkPythonCommand::Execute(vtkObject* ptr, unsigned long eventtype, void* ca
     arglist = Py_BuildValue("(Ns)", obj2, eventname);
   }
 
-  PyObject* result = PyEval_CallObject(this->obj, arglist);
+  PyObject* result = PyObject_Call(this->obj, arglist, nullptr);
   Py_DECREF(arglist);
 
   if (result)

Wrapping/PythonCore/vtkPythonUtil.cxx

@@ -564,7 +564,7 @@ vtkObjectBase* vtkPythonUtil::GetPointerFromObject(PyObject* obj, const char* re
     if (obj)
     {
       PyObject* arglist = Py_BuildValue("()");
-      PyObject* result = PyEval_CallObject(obj, arglist);
+      PyObject* result = PyObject_Call(obj, arglist, nullptr);
       Py_DECREF(arglist);
       Py_DECREF(obj);
       if (result == nullptr)
@@ -1083,7 +1083,7 @@ void vtkPythonVoidFunc(void* arg)
 
   arglist = Py_BuildValue("()");
 
-  result = PyEval_CallObject(func, arglist);
+  result = PyObject_Call(func, arglist, nullptr);
   Py_DECREF(arglist);
 
   if (result)