Join the queue thread after closing it in tests

tests/test_functional.py

@@ -98,9 +98,10 @@ def stop_subprocess(self):
             self.proc.terminate()
         self.sock.close()
         # This give us one FD back ...
-        self.queue.close()
         self.proc.join()
         self.proc.close()
+        self.queue.close()
+        self.queue.join_thread()
 
         # The following is for the benefit of PyPy 3, for some reason it is
         # holding on to some resources way longer than necessary causing tests
@@ -109,6 +110,7 @@ def stop_subprocess(self):
         # increase the limits before running tests, this works as well and
         # means we don't need to remember to do that.
         import gc
+
         gc.collect()
 
     def assertline(self, line, status, reason, version):