PEP 466: backport persistent urandom fd (closes #21305)

Patch from Alex Gaynor.
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 748a63b..05bb62b 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -536,6 +536,7 @@
     PyInt_Fini();
     PyFloat_Fini();
     PyDict_Fini();
+    _PyRandom_Fini();
 
 #ifdef Py_USING_UNICODE
     /* Cleanup Unicode implementation */