multiprocessing.queues.SimpleQueue should have a close() method.  This is needed to explicitly release the two file descriptors of the Pipe used internally.  Without it, the file descriptors leak if a reference to the SimpleQueue object happens to stay around for longer than expected (e.g. in a reference cycle, or with PyPy).

I think the following would do:

diff -r 0b72fd1a7641 lib-python/2.7/multiprocessing/queues.py
--- a/lib-python/2.7/multiprocessing/queues.py  Sun Jul 16 13:41:28 2017 +0200
+++ b/lib-python/2.7/multiprocessing/queues.py  Wed Jul 19 10:45:03 2017 +0200
@@ -358,6 +358,11 @@
             self._wlock = Lock()
         self._make_methods()

+    def close(self):
+        # PyPy extension: CPython doesn't have this method!
+        self._reader.close()
+        self._writer.close()
+
     def empty(self):
         return not self._reader.poll()