Mark Hammond: For Windows debug builds, we now only offer to dump

remaining object references if the environment variable PYTHONDUMPREFS
exists.  The default behaviour caused problems for background or
otherwise invisible processes that use the debug build of Python.

Python/pythonrun.c

@@ -242,7 +242,11 @@ Py_Finalize()
 #endif
 
 #ifdef Py_TRACE_REFS
-	if (_Py_AskYesNo("Print left references?")) {
+	if (
+#ifdef MS_WINDOWS /* Only ask on Windows if env var set */
+	    getenv("PYTHONDUMPREFS") &&
+#endif /* MS_WINDOWS */
+	    _Py_AskYesNo("Print left references?")) {
 		_Py_PrintReferences(stderr);
 	}
 #endif /* Py_TRACE_REFS */