werkzeug server failed to handle request - gevent

Question

I'm trying to run this gevent server
from gevent import pywsgi
from Index import application
import paste.urlparser
import os
# http server: serves up static files
print "static files",os.path.dirname(__file__)
print "serving on localhost:8000"
http_server = pywsgi.WSGIServer(
('', 8000),
paste.urlparser.StaticURLParser(os.path.dirname(__file__)))
print 'Serving on https://127.0.0.1:4000'
server = pywsgi.WSGIServer(('0.0.0.0', 4000), application,spawn=None)
# Start the server greenlets
http_server.start()
# to start the server asynchronously, call server.start()
# we use blocking serve_forever() here because we have no other jobs
server.serve_forever()
I'm getting this exception where it gives me failed to handle request from werkzeug server.
I've used only werkzeug utility and have never used werkzeug server..
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/gevent/server.py", line 131, in _do_accept
self._handle(client_socket, address)
File "/usr/local/lib/python2.7/dist-packages/gevent/pywsgi.py", line 571, in handle
handler.handle()
File "/usr/local/lib/python2.7/dist-packages/gevent/pywsgi.py", line 180, in handle
result = self.handle_one_request()
File "/usr/local/lib/python2.7/dist-packages/gevent/pywsgi.py", line 287, in handle_one_request
raw_requestline = self.read_requestline()
File "/usr/local/lib/python2.7/dist-packages/gevent/pywsgi.py", line 280, in read_requestline
return self.rfile.readline(MAX_REQUEST_LINE)
File "/usr/lib/python2.7/socket.py", line 476, in readline
data = self._sock.recv(self._rbufsize)
File "/usr/local/lib/python2.7/dist-packages/gevent/socket.py", line 432, in recv
wait_read(sock.fileno(), timeout=self.timeout, event=self._read_event)
File "/usr/local/lib/python2.7/dist-packages/gevent/socket.py", line 169, in wait_read
switch_result = get_hub().switch()
File "/usr/local/lib/python2.7/dist-packages/gevent/hub.py", line 154, in switch
assert cur is not self, 'Cannot switch to MAINLOOP from MAINLOOP'
AssertionError: Cannot switch to MAINLOOP from MAINLOOP
<WSGIServer fileno=4 address=0.0.0.0:4000>: Failed to handle request from ('127.0.0.1', 36088)