Gevent thread exclusion

When I ran the code below, this error appears for a long time.

code:

from gevent import monkey; monkey.patch_all()
from gevent.pywsgi import WSGIServer 
sys.modules.pop("threading", None) 

      

        
        
        
      

    

Exception information:

Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/gevent/greenlet.py", line 375, in _notify_links
    link(self)
  File "/usr/local/lib/python2.7/dist-packages/gevent/threading.py", line 22, in _cleanup
    __threading__._active.pop(id(g))
KeyError: 40406544
(<function _cleanup at 0x1fed0c8>, <Greenlet at 0x2688e10>) failed with KeyError