Update futures to 3.2.0

libs/concurrent/futures/process.py

@@ -43,20 +43,14 @@ Process #1..n:
   _ResultItems in "Request Q"
 """
 
-from __future__ import with_statement
 import atexit
+from concurrent.futures import _base
+import Queue as queue
 import multiprocessing
 import threading
 import weakref
 import sys
 
-from concurrent.futures import _base
-
-try:
-    import queue
-except ImportError:
-    import Queue as queue
-
 __author__ = 'Brian Quinlan (brian@sweetapp.com)'
 
 # Workers are created as daemon threads and processes. This is done to allow the
@@ -79,11 +73,11 @@ _shutdown = False
 def _python_exit():
     global _shutdown
     _shutdown = True
-    items = list(_threads_queues.items())
+    items = list(_threads_queues.items()) if _threads_queues else ()
     for t, q in items:
         q.put(None)
     for t, q in items:
-        t.join()
+        t.join(sys.maxint)
 
 # Controls how many more calls than processes will be queued in the call queue.
 # A smaller number will mean that processes spend more time idle waiting for
@@ -132,7 +126,7 @@ def _process_worker(call_queue, result_queue):
             return
         try:
             r = call_item.fn(*call_item.args, **call_item.kwargs)
-        except BaseException:
+        except:
             e = sys.exc_info()[1]
             result_queue.put(_ResultItem(call_item.work_id,
                                          exception=e))
@@ -220,6 +214,8 @@ def _queue_management_worker(executor_reference,
                 work_item.future.set_exception(result_item.exception)
             else:
                 work_item.future.set_result(result_item.result)
+            # Delete references to object. See issue16284
+            del work_item
         # Check whether we should start shutting down.
         executor = executor_reference()
         # No more work items can be added if:
@@ -266,6 +262,7 @@ def _check_system_limits():
     _system_limited = "system provides too few semaphores (%d available, 256 necessary)" % nsems_max
     raise NotImplementedError(_system_limited)
 
+
 class ProcessPoolExecutor(_base.Executor):
     def __init__(self, max_workers=None):
         """Initializes a new ProcessPoolExecutor instance.
@@ -280,6 +277,9 @@ class ProcessPoolExecutor(_base.Executor):
         if max_workers is None:
             self._max_workers = multiprocessing.cpu_count()
         else:
+            if max_workers <= 0:
+                raise ValueError("max_workers must be greater than 0")
+
             self._max_workers = max_workers
 
         # Make the call queue slightly larger than the number of processes to
@@ -351,7 +351,7 @@ class ProcessPoolExecutor(_base.Executor):
             # Wake up queue management thread
             self._result_queue.put(None)
             if wait:
-                self._queue_management_thread.join()
+                self._queue_management_thread.join(sys.maxint)
         # To reduce the risk of openning too many files, remove references to
         # objects that use file descriptors.
         self._queue_management_thread = None