no se puede enviar el error al usar la biblioteca bitcoin de python para enviar bitcoin en testnet

Cuando ejecuto el script

from bitcoin.core import COIN, b2lx
import bitcoin.wallet
import bitcoin.rpc

rpc = bitcoin.rpc.Proxy()
addr = bitcoin.wallet.CBitcoinAddress('mfrMeTKojpEXFXpcQiRr7zA3Bff4UBgZTx')

txid = rpc.sendtoaddress(addr, 0.001 * COIN)
print(b2lx(txid))

Obtuve el siguiente error

CannotSendRequest                         Traceback (most recent call last)
<ipython-input-23-904d1d3102d7> in <module>()
----> 1 txid = rpc.sendtoaddress(addr, 0.001 * COIN)

/home/remote_user/unix_practice/python-bitcoinlib/bitcoin/rpc.py in sendtoaddress(self, addr, amount)
    557         addr = str(addr)
    558         amount = float(amount)/COIN
--> 559         r = self._call('sendtoaddress', addr, amount)
    560         return lx(r)
    561 

/home/remote_user/unix_practice/python-bitcoinlib/bitcoin/rpc.py in _call(self, service_name, *args)
    150                              'User-Agent': DEFAULT_USER_AGENT,
    151                              'Authorization': self.__auth_header,
--> 152                              'Content-type': 'application/json'})
    153 
    154         response = self._get_response()

/usr/lib64/python2.7/httplib.pyc in request(self, method, url, body, headers)
    971     def request(self, method, url, body=None, headers={}):
    972         """Send a complete request to the server."""
--> 973         self._send_request(method, url, body, headers)
    974 
    975     def _set_content_length(self, body):

/usr/lib64/python2.7/httplib.pyc in _send_request(self, method, url, body, headers)
    999             skips['skip_accept_encoding'] = 1
   1000 
-> 1001         self.putrequest(method, url, **skips)
   1002 
   1003         if body is not None and 'content-length' not in header_names:

/usr/lib64/python2.7/httplib.pyc in putrequest(self, method, url, skip_host, skip_accept_encoding)
    869             self.__state = _CS_REQ_STARTED
    870         else:
--> 871             raise CannotSendRequest()
    872 
    873         # Save the method we use, we need it later in the response phase

CannotSendRequest:

¿Alguna idea de cómo resolver esto? Usé el código de

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