Python3:gevent:greenlet.error: cannot switch to a different thread


2020-08-01 22:06:12:034678: ----------------------------------------
2020-08-01 22:06:50:875038: Exception happened during processing of request from ('127.0.0.1', 55207)
2020-08-01 22:06:50:875038: Traceback (most recent call last):
2020-08-01 22:06:50:884013:   File "e:\python36\lib\socketserver.py", line 654, in process_request_thread
2020-08-01 22:06:50:885011:     self.finish_request(request, client_address)
2020-08-01 22:06:50:885011:   File "e:\python36\lib\socketserver.py", line 364, in finish_request
2020-08-01 22:06:50:885011:     self.RequestHandlerClass(request, client_address, self)
2020-08-01 22:06:50:885011:   File "e:\python36\lib\socketserver.py", line 724, in __init__
2020-08-01 22:06:50:885011:     self.handle()
2020-08-01 22:06:50:885011:   File "E:\work_space\warclouds\version01\openstack_api_server\venv\lib\site-packages\werkzeug\serving.py", line 345, in handle
2020-08-01 22:06:50:885011:     BaseHTTPRequestHandler.handle(self)
2020-08-01 22:06:50:885011:   File "e:\python36\lib\http\server.py", line 418, in handle
2020-08-01 22:06:50:885011:     self.handle_one_request()
2020-08-01 22:06:50:885011:   File "E:\work_space\warclouds\version01\openstack_api_server\venv\lib\site-packages\werkzeug\serving.py", line 375, in handle_one_request
2020-08-01 22:06:50:885011:     self.raw_requestline = self.rfile.readline()
2020-08-01 22:06:50:885011:   File "e:\python36\lib\socket.py", line 586, in readinto
2020-08-01 22:06:50:885011:     return self._sock.recv_into(b)
2020-08-01 22:06:50:885011:   File "e:\python36\lib\site-packages\gevent\_socket3.py", line 502, in recv_into
2020-08-01 22:06:50:885011:     self._wait(self._read_event)
2020-08-01 22:06:50:885011:   File "src\\gevent\\_hub_primitives.py", line 317, in gevent._gevent_c_hub_primitives.wait_on_socket
2020-08-01 22:06:50:885011:   File "src\\gevent\\_hub_primitives.py", line 322, in gevent._gevent_c_hub_primitives.wait_on_socket
2020-08-01 22:06:50:885011:   File "src\\gevent\\_hub_primitives.py", line 304, in gevent._gevent_c_hub_primitives._primitive_wait
2020-08-01 22:06:50:885011:   File "src\\gevent\\_hub_primitives.py", line 46, in gevent._gevent_c_hub_primitives.WaitOperationsGreenlet.wait
2020-08-01 22:06:50:885011:   File "src\\gevent\\_hub_primitives.py", line 46, in gevent._gevent_c_hub_primitives.WaitOperationsGreenlet.wait
2020-08-01 22:06:50:885011:   File "src\\gevent\\_hub_primitives.py", line 55, in gevent._gevent_c_hub_primitives.WaitOperationsGreenlet.wait
2020-08-01 22:06:50:885011:   File "src\\gevent\\_waiter.py", line 151, in gevent._gevent_c_waiter.Waiter.get
2020-08-01 22:06:50:885011:   File "src\\gevent\\_greenlet_primitives.py", line 61, in gevent._gevent_c_greenlet_primitives.SwitchOutGreenletWithLoop.switch
2020-08-01 22:06:50:885011:   File "src\\gevent\\_greenlet_primitives.py", line 61, in gevent._gevent_c_greenlet_primitives.SwitchOutGreenletWithLoop.switch
2020-08-01 22:06:50:885011:   File "src\\gevent\\_greenlet_primitives.py", line 65, in gevent._gevent_c_greenlet_primitives.SwitchOutGreenletWithLoop.switch
2020-08-01 22:06:50:886007:   File "src\\gevent\\_gevent_c_greenlet_primitives.pxd", line 35, in gevent._gevent_c_greenlet_primitives._greenlet_switch
2020-08-01 22:06:50:889000: greenlet.error: cannot switch to a different thread
2020-08-01 22:06:50:889000: ----------------------------------------