Availability check traceback

availability.log

Ursula(0x26FD316) >>> Unhandled error in Deferred:

Traceback (most recent call last):
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/twisted/internet/base.py", line 1283, in run
    self.mainLoop()
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/twisted/internet/base.py", line 1292, in mainLoop
    self.runUntilCurrent()
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/twisted/internet/base.py", line 913, in runUntilCurrent
    call.func(*call.args, **call.kw)
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/twisted/internet/task.py", line 239, in __call__
    d = defer.maybeDeferred(self.f, *self.a, **self.kw)
--- <exception caught here> ---
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/twisted/internet/defer.py", line 654, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "/home/ubuntu/nucypher/nucypher/network/protocols.py", line 173, in handle_measurement_errors
    failure.raiseException()
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/twisted/python/failure.py", line 488, in raiseException
    raise self.value.with_traceback(self.tb)
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/twisted/internet/defer.py", line 151, in maybeDeferred
    result = f(*args, **kw)
  File "/home/ubuntu/nucypher/nucypher/network/protocols.py", line 209, in maintain
    result = self.measure()
  File "/home/ubuntu/nucypher/nucypher/network/protocols.py", line 240, in measure
    responding_ursula=ursula)
  File "/home/ubuntu/nucypher/nucypher/network/middleware.py", line 215, in check_rest_availability
    certificate_filepath=certificate_filepath)
  File "/home/ubuntu/nucypher/nucypher/network/middleware.py", line 101, in method_wrapper
    response = self.invoke_method(method, url, verify=certificate_filepath, *args, **kwargs)
  File "/home/ubuntu/nucypher/nucypher/network/middleware.py", line 67, in invoke_method
    response = method(url, *args, **kwargs)
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/requests/api.py", line 116, in post
    return request('post', url, data=data, json=json, **kwargs)
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/requests/api.py", line 60, in request
    return session.request(method=method, url=url, **kwargs)
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/requests/sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/requests/sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/requests/adapters.py", line 416, in send
    self.cert_verify(conn, request.url, verify, cert)
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/requests/adapters.py", line 215, in cert_verify
    if url.lower().startswith('https') and verify:
  File "/home/ubuntu/.local/share/virtualenvs/nucypher-fvStivKV/lib/python3.6/site-packages/constant_sorrow/constants.py", line 68, in __bool__
    raise TypeError("The constant {} does not have a boolean representation.".format(self.__class__.__name__))
builtins.TypeError: The constant CERTIFICATE_NOT_SAVED does not have a boolean representation.