Fixed the warnings from pylint.

BUG=None
TEST=None

Change-Id: I1b2b5df85eacb1b30557d108bf982054ea5e3cea
Reviewed-on: https://gerrit-int.chromium.org/39812
Reviewed-by: Luis Lozano <llozano@chromium.org>
Commit-Queue: Yuheng Long <yuhenglong@google.com>
Tested-by: Yuheng Long <yuhenglong@google.com>
diff --git a/bestflags/pipeline_process.py b/bestflags/pipeline_process.py
index 21d3c58..37f4a99 100644
--- a/bestflags/pipeline_process.py
+++ b/bestflags/pipeline_process.py
@@ -81,7 +81,7 @@
     """
 
     # the worker pool
-    self._pool = multiprocessing.Pool(self._num_processes)
+    work_pool = multiprocessing.Pool(self._num_processes)
 
     # the helper process
     helper_process = multiprocessing.Process(target=self._helper,
@@ -106,13 +106,13 @@
         self._helper_queue.put(task)
       else:
         # Let the workers do the actual work.
-        self._pool.apply_async(self._worker, args=(task, self._work_queue,
+        work_pool.apply_async(self._worker, args=(task, self._work_queue,
                                                    self._result_queue))
         mycache.append(task_key)
 
     # Shutdown the workers pool and the helper process.
-    self._pool.close()
-    self._pool.join()
+    work_pool.close()
+    work_pool.join()
 
     self._helper_queue.put(POISONPILL)
     helper_process.join()