[3.15] gh-158539: Use portable static assertion messages

Author: pablogsal

Modules/_remote_debugging/threads.c

@@ -23,9 +23,11 @@
 /* Derive unexported offsets from adjacent fields to keep the debug-offset
  * table compatible across patch releases. */
 static_assert(offsetof(PyThreadState, exc_info) ==
-              offsetof(PyThreadState, current_exception) + sizeof(uintptr_t));
+              offsetof(PyThreadState, current_exception) + sizeof(uintptr_t),
+              "exc_info must immediately follow current_exception");
 static_assert(offsetof(_PyErr_StackItem, previous_item) ==
-              offsetof(_PyErr_StackItem, exc_value) + sizeof(uintptr_t));
+              offsetof(_PyErr_StackItem, exc_value) + sizeof(uintptr_t),
+              "previous_item must immediately follow exc_value");
 
 /* ============================================================================
  * THREAD ITERATION FUNCTIONS