fix key error
fix error cause use the fault Queue Class when running in a multiprocess env
import Empty for compatiable with either threading module or multiprocessing module
fix typo
that is a bug.
should use the "get" function as block-method otherwise processes or threads may exit when still have tasks in queue as a mistake.
set it as block-method and setup a timeout parm will solve the problem.
make producer and cusumer work concurrently