bpo-33932: Calling Py_Initialize() twice does nothing (GH-7845)

Calling Py_Initialize() twice does nothing, instead of failing with a
fatal error: restore the Python 3.6 behaviour.
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 958219b..9bf0ebd 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -892,6 +892,11 @@
 _PyInitError
 _Py_InitializeEx_Private(int install_sigs, int install_importlib)
 {
+    if (_PyRuntime.initialized) {
+        /* bpo-33932: Calling Py_Initialize() twice does nothing. */
+        return _Py_INIT_OK();
+    }
+
     _PyCoreConfig config = _PyCoreConfig_INIT;
     _PyInitError err;