# Buggy code
def stop_learning_loop(self, reason=None):
    """
    Only for tests at this point.  Maybe some day for graceful shutdowns.
    """
    self._learning_task.stop()


# Traceback (ValueError)
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]: Unhandled error in Deferred:
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]: Traceback (most recent call last):
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher-venv/lib/python3.6/site-packages/twisted/internet/base.py", line 1283, in run
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     self.mainLoop()
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher-venv/lib/python3.6/site-packages/twisted/internet/base.py", line 1292, in mainLoop
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     self.runUntilCurrent()
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher-venv/lib/python3.6/site-packages/twisted/internet/base.py", line 913, in runUntilCurrent
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     call.func(*call.args, **call.kw)
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher-venv/lib/python3.6/site-packages/twisted/internet/task.py", line 239, in __call__
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     d = defer.maybeDeferred(self.f, *self.a, **self.kw)
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]: --- <exception caught here> ---
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher-venv/lib/python3.6/site-packages/twisted/internet/defer.py", line 654, in _runCallbacks
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     current.result = callback(current.result, *args, **kw)
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher/nucypher/network/sensors.py", line 89, in handle_measurement_errors
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     failure.raiseException()
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher-venv/lib/python3.6/site-packages/twisted/python/failure.py", line 488, in raiseException
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     raise self.value.with_traceback(self.tb)
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher-venv/lib/python3.6/site-packages/twisted/internet/defer.py", line 151, in maybeDeferred
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     result = f(*args, **kw)
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher/nucypher/network/sensors.py", line 138, in maintain
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     self.measure()
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher/nucypher/network/sensors.py", line 191, in measure
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     certificate_filepath=certificate_filepath)
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher/nucypher/network/middleware.py", line 248, in check_rest_availability
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     certificate_filepath=certificate_filepath)
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:   File "/home/ubuntu/nucypher/nucypher/network/middleware.py", line 114, in method_wrapper
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]:     raise ValueError("Don't try to pass a node with a certificate_filepath while also passing a"
Apr 02 17:02:28 ip-172-31-19-8 nucypher[29582]: builtins.ValueError: Don't try to pass a node with a certificate_filepath while also passing a different certificate_filepath.  What do you even expect?
Apr 03 00:02:29 ip-172-31-19-8 nucypher[29582]: Broadcasting CONFIRMACTIVITY Transaction (264369 gwei @ 3000000000)...

# Fixed code
def stop_learning_loop(self, reason=None):
    """
    Only for tests at this point.  Maybe some day for graceful shutdowns.
    """
    if self._learning_task.running:
        self._learning_task.stop()