Caldav error

Configuration
1

since update to 0.95.4 my caldav integration is not working anymore
Following error message:

Error while setting up platform caldav
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/vobject/base.py", line 529, in __getattr__
    return self.contents[toVName(name)][0]
KeyError: 'vevent'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/entity_platform.py", line 126, in _async_setup_platform
    SLOW_SETUP_MAX_WAIT)
  File "/usr/local/lib/python3.7/asyncio/tasks.py", line 416, in wait_for
    return fut.result()
  File "/usr/local/lib/python3.7/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/src/homeassistant/homeassistant/components/caldav/calendar.py", line 84, in setup_platform
    cust_calendar.get(CONF_SEARCH)))
  File "/usr/src/homeassistant/homeassistant/components/caldav/calendar.py", line 106, in __init__
    super().__init__(hass, device_data)
  File "/usr/src/homeassistant/homeassistant/components/calendar/__init__.py", line 83, in __init__
    self.update()
  File "/usr/src/homeassistant/homeassistant/components/calendar/__init__.py", line 149, in update
    if not self.data or not self.data.update():
  File "/usr/src/homeassistant/homeassistant/util/__init__.py", line 224, in wrapper
    result = method(*args, **kwargs)
  File "/usr/src/homeassistant/homeassistant/components/caldav/calendar.py", line 172, in update
    results.sort(key=lambda x: self.to_datetime(
  File "/usr/src/homeassistant/homeassistant/components/caldav/calendar.py", line 173, in <lambda>
    x.instance.vevent.dtstart.value
  File "/usr/local/lib/python3.7/site-packages/vobject/base.py", line 531, in __getattr__
    raise AttributeError(name)
AttributeError: vevent
2

If you have this error at the end of your error lines:

At line 29: DURATION must have a single duration string

That means you have at least one event which has DTSTART and DTEND having the same time; that is a ‘Zero Time’ event. I don’t know why it was never corrected in icalendar.py (This has been an issue since 2015). Anyway, if your start and end time are the same on any event, try to set end time at least 1 min forward of start time. That solved my problem.