sys.getfilesystemencoding() raises a RuntimeError if initfsencoding() was not

called yet: detect bootstrap (startup) issues earlier.

Misc/NEWS

@@ -49,6 +49,9 @@ Core and Builtins
 Library
 -------
 
+- sys.getfilesystemencoding() raises a RuntimeError if initfsencoding() was not
+  called yet: detect bootstrap (startup) issues earlier.
+
 - Issue #11618: Fix the timeout logic in threading.Lock.acquire() under Windows.
 
 - Issue #11256: Fix inspect.getcallargs on functions that take only keyword

Python/sysmodule.c

@@ -259,8 +259,9 @@ sys_getfilesystemencoding(PyObject *self)
 {
     if (Py_FileSystemDefaultEncoding)
         return PyUnicode_FromString(Py_FileSystemDefaultEncoding);
-    Py_INCREF(Py_None);
-    return Py_None;
+    PyErr_SetString(PyExc_RuntimeError,
+                    "filesystem encoding is not initialized");
+    return NULL;
 }
 
 PyDoc_STRVAR(getfilesystemencoding_doc,