Config invalid - and no idea what to do to solve it :)

Configuration
1

I got this strange config error after upgrading HA OS to the latest release. Nothing else changed, and I have no idea where it comes from, and how to solve it …

Can anybody please help me? Thanks!

Platform error switch.tasmota - cannot import name 'CONF_AVAILABILITY_TOPIC' from 'homeassistant.components.mqtt' (/usr/src/homeassistant/homeassistant/components/mqtt/__init__.py)
Platform error switch.tasmota - cannot import name 'CONF_AVAILABILITY_TOPIC' from 'homeassistant.components.mqtt' (/usr/src/homeassistant/homeassistant/components/mqtt/__init__.py)
Platform error switch.tasmota - cannot import name 'CONF_AVAILABILITY_TOPIC' from 'homeassistant.components.mqtt' (/usr/src/homeassistant/homeassistant/components/mqtt/__init__.py)
Platform error switch.tasmota - cannot import name 'CONF_AVAILABILITY_TOPIC' from 'homeassistant.components.mqtt' (/usr/src/homeassistant/homeassistant/components/mqtt/__init__.py)
Platform error switch.tasmota - cannot import name 'CONF_AVAILABILITY_TOPIC' from 'homeassistant.components.mqtt' (/usr/src/homeassistant/homeassistant/components/mqtt/__init__.py)
Platform error switch.tasmota - cannot import name 'CONF_AVAILABILITY_TOPIC' from 'homeassistant.components.mqtt' (/usr/src/homeassistant/homeassistant/components/mqtt/__init__.py)