集成gunicorn+flask+twisted，其中：
- gunicorn做web server
- flask做web framework
- twisted做后台socket通讯
出现如下错误：
Unexpected error in main loop.exceptions.SystemExit: 1
2019-03-01 16:22:19+0800 [-] Unhandled Error
Traceback (most recent call last):
File "/usr/lib/python2.7/site-packages/gunicorn/util.py", line 350, in import_app
__import__(module)
File "/home/p-api/papiflask.py", line 6, in <module>
import papirpcclient
File "/home/p-api/papirpcclient.py", line 178, in <module>
reactor.run()
File "/usr/lib64/python2.7/site-packages/twisted/internet/base.py", line 1267, in run
self.mainLoop()
--- <exception caught here> ---
File "/usr/lib64/python2.7/site-packages/twisted/internet/base.py", line 1279, in mainLoop
self.doIteration(t)
File "/usr/lib64/python2.7/site-packages/twisted/internet/epollreactor.py", line 218, in doPoll
l = self._poller.poll(timeout, len(self._selectables))
File "/usr/lib/python2.7/site-packages/gunicorn/workers/gthread.py", line 112, in handle_quit
sys.exit(0)
exceptions.SystemExit: 0
[2019-03-01 16:22:20 +0000] [18372] [INFO] Shutting down: Master