fix resource tracker leak

Author: luccabb

Lib/multiprocessing/resource_tracker.py

@@ -212,6 +212,9 @@ def _send(self, cmd, name, rtype):
         assert nbytes == len(msg), "nbytes {0:n} but len(msg) {1:n}".format(
             nbytes, len(msg))
 
+    def __del__(self):
+        self._stop()
+
 
 _resource_tracker = ResourceTracker()
 ensure_running = _resource_tracker.ensure_running