Issue #18756: os.urandom() now uses a lazily-opened persistent file descriptor, so as to avoid using many file descriptors when run in parallel from multiple threads.

Python/pythonrun.c

@@ -625,6 +625,7 @@ Py_Finalize(void)
     PyDict_Fini();
     PySlice_Fini();
     _PyGC_Fini();
+    _PyRandom_Fini();
 
     /* Cleanup Unicode implementation */
     _PyUnicode_Fini();