ExceptionIgnored error: SIGALRM Timeout handler

Question

I made a custom timeout handler using the SIGALRM signal but very rarely I get an error saying that TimeoutException was 'ignored'.

Timeout handler code:

def timeout_handler(signum, frame):
    raise TimeoutException

signal.signal(signal.SIGALRM, timeout_handler)


camera_stream = ThreadedCamera() # Separate Thread updating image
while True:
    try:
        while True:
            signal.alarm(5) # start 5s timer
            send_image(camera_stream.image) # function is blocked if it doesnt finish within 5 seconds
            signal.alarm(0) # end timer
    except TimeoutException:
        print("timeout")
        time.sleep(5)

Error:

Exception ignored in: <function Context.__del__ at 0x7f93e
Traceback (most recent call last):
File "zmq/sugar/context.py", line 71, in __del__
File "zmq/sugar/context.py", line 190, in term
File "zmq/backend/cython/context.pyx", line 82, in zmq.backend.cyt
File "zmq/backend/cython/checkrc.pxd", line 13, in zmq.backend.cyt
File "camera_client.py", line 22, in timeout_handler
__main__.TimeoutException:

It seems like my try/except statement should catch the TimeouteException considering the alarm is cancelled before I exit the try/except. Is it possible that the camera in the separate thread is somehow catching this error? Any help would be greatly appreciated!