workaround AssertionError <Finalize, dead>

src/core/backends.py

@@ -5,7 +5,7 @@
 from collections import deque
 import traceback
 import time
-
+import gc
 #logger = multiprocessing.log_to_stderr()
 #logger.setLevel(multiprocessing.SUBDEBUG)
 
@@ -170,6 +170,11 @@ def start(self):
         self.JoinedProcesses.value = 0
         self.guardDead.clear()
 
+        # collect the garbages before forking so that the left-over
+        # junk won't throw out assertion errors due to
+        # wrong pid in multiprocess.heap
+        gc.collect()
+
         map(lambda x: x.start(), self.P)
 
         # p is alive from the moment start returns.