error during exceptions on event observer

[gnzsnz]

when observer raises an exception and there is no error_event, logging fails

    def __call__(self, caller, *args, **kwargs):
        """Loop over all active callbacks and call them"""
        for slot in self.slots.copy():
            ref = slot.weakref
            func = slot.func

            try:
                if ref:
                    obj = ref()
                else:
                    obj = slot.obj

                result = None
                if obj is None:
                    if func:
                        result = func(*args, **kwargs)
                else:
                    if func:
                        result = func(obj, *args, **kwargs)
                    else:
                        result = obj(*args, **kwargs)

                # even though asyncio.iscoroutine() would also work here,
                # this manual hasattr() check performs better.
                if result and hasattr(result, "__await__"):
                    asyncio.ensure_future(result, loop=get_event_loop())
            except Exception as error:
                # It's not really clear in the documentation or usage that exceptions
                # get returned via an 'error_event' callback. We should make sure
                # people know this clearly so event handler callback errors are noticed.
                if len(caller.error_event):
                    caller.error_event.emit(caller, error)
                else:
>                   Event.logger.exception(
                        f"Value {args} caused exception for event {caller}"
                    )
E                   AttributeError: type object 'Event' has no attribute 'logger'

eventkit/event.py:112: AttributeError

[gnzsnz]

fix on 2bca019