Error in the log: 1 positional argument but 2 were given

Anyone having a clue to what this means, or, even better, where to find the error source…?

2018-09-10 22:32:58 ERROR (MainThread) [homeassistant.core] Error doing job: Future exception was never retrieved
Traceback (most recent call last):
File “/usr/local/lib/python3.6/concurrent/futures/thread.py”, line 56, in run
result = self.fn(*self.args, **self.kwargs)
File “/usr/local/lib/python3.6/site-packages/homeassistant/util/init.py”, line 325, in wrapper
result = method(*args, **kwargs)
TypeError: update() takes 1 positional argument but 2 were given