bpo-38631: Add _Py_NO_RETURN to functions calling Py_FatalError() (GH-18278)

Add _Py_NO_RETURN to functions calling Py_FatalError():

* _PyObject_AssertFailed()
* dummy_dealloc()
* faulthandler_fatal_error_thread()
* none_dealloc()
* notimplemented_dealloc()
diff --git a/Include/cpython/object.h b/Include/cpython/object.h
index 75e5599..dc8fd6f 100644
--- a/Include/cpython/object.h
+++ b/Include/cpython/object.h
@@ -443,7 +443,7 @@
    NDEBUG against a Python built with NDEBUG defined.
 
    msg, expr and function can be NULL. */
-PyAPI_FUNC(void) _PyObject_AssertFailed(
+PyAPI_FUNC(void) _Py_NO_RETURN _PyObject_AssertFailed(
     PyObject *obj,
     const char *expr,
     const char *msg,
diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
index b19401e..555e1af 100644
--- a/Modules/faulthandler.c
+++ b/Modules/faulthandler.c
@@ -1065,24 +1065,10 @@
     Py_RETURN_NONE;
 }
 
-static void
+static void _Py_NO_RETURN
 faulthandler_fatal_error_thread(void *plock)
 {
-#ifndef __clang__
-    PyThread_type_lock *lock = (PyThread_type_lock *)plock;
-#endif
-
     Py_FatalError("in new thread");
-
-#ifndef __clang__
-    /* Issue #28152: Py_FatalError() is declared with
-       __attribute__((__noreturn__)).  GCC emits a warning without
-       "PyThread_release_lock()" (compiler bug?), but Clang is smarter and
-       emits a warning on the return. */
-
-    /* notify the caller that we are done */
-    PyThread_release_lock(lock);
-#endif
 }
 
 static PyObject *
diff --git a/Objects/object.c b/Objects/object.c
index c5d28e5..67a6386 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -1646,7 +1646,7 @@
 }
 
 /* ARGUSED */
-static void
+static void _Py_NO_RETURN
 none_dealloc(PyObject* ignore)
 {
     /* This should never get called, but we also don't want to SEGV if
@@ -1784,7 +1784,7 @@
     Py_RETURN_NOTIMPLEMENTED;
 }
 
-static void
+static void _Py_NO_RETURN
 notimplemented_dealloc(PyObject* ignore)
 {
     /* This should never get called, but we also don't want to SEGV if
@@ -2225,7 +2225,7 @@
 }
 
 
-void
+void _Py_NO_RETURN
 _PyObject_AssertFailed(PyObject *obj, const char *expr, const char *msg,
                        const char *file, int line, const char *function)
 {
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 924885d..bb7c0b8 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -2529,7 +2529,7 @@
     return PyUnicode_FromString("<dummy key>");
 }
 
-static void
+static void _Py_NO_RETURN
 dummy_dealloc(PyObject* ignore)
 {
     Py_FatalError("deallocating <dummy key>");