Template weather integration throws ValueError: dictionary update sequence element #0 has length 1; 2 is required

Configuration
1

using a first config like:

  - platform: template
    name: Composite
    condition_template: >
      {{states('sensor.br_condition')}}
    temperature_template: >
      {{states('sensor.weatherbit_apparent_temperature')|float}}
    humidity_template: >
      {{states('sensor.weatherbit_humidity')|float}}
    forecast_template: >
      {{state_attr('weather.buienradar','forecast')}}
    pressure_template: >
      {{states('sensor.luftdaten_37248_pressure')}}
    wind_speed_template: >
      {{states('sensor.openweathermap_wind_speed')|float}}

all of which templates are correct and display their values in the template editor, this error is throes in the log

Logger: homeassistant.helpers.event
Source: components/weather/__init__.py:181 
First occurred: 1:51:43 PM (2 occurrences) 
Last logged: 1:51:46 PM

Error while processing state change for sensor.openweathermap_wind_speed
Error while processing state change for sensor.luftdaten_37248_pressure
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/helpers/event.py", line 280, in _async_state_change_dispatcher
    hass.async_run_hass_job(job, event)
  File "/usr/src/homeassistant/homeassistant/core.py", line 435, in async_run_hass_job
    hassjob.target(*args)
  File "/usr/src/homeassistant/homeassistant/helpers/event.py", line 1005, in _refresh
    self.hass.async_run_hass_job(self._job, event, updates)
  File "/usr/src/homeassistant/homeassistant/core.py", line 435, in async_run_hass_job
    hassjob.target(*args)
  File "/usr/src/homeassistant/homeassistant/components/template/template_entity.py", line 251, in _handle_results
    self.async_write_ha_state()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 295, in async_write_ha_state
    self._async_write_ha_state()
  File "/usr/src/homeassistant/homeassistant/helpers/entity.py", line 321, in _async_write_ha_state
    attr.update(self.state_attributes or {})
  File "/usr/src/homeassistant/homeassistant/components/weather/__init__.py", line 181, in state_attributes
    forecast_entry = dict(forecast_entry)
ValueError: dictionary update sequence element #0 has length 1; 2 is required

while the 2 mentioned offenders sensor.openweathermap_wind_speed
and sensor.luftdaten_37248_pressure are correct:

Schermafbeelding 2021-03-12 om 13.56.02
Schermafbeelding 2021-03-12 om 13.56.021958×1216 401 KB

what could be wrong here?

por is it the forecast template, taking that out check the config valid, as does rewriting it like

forecast_template: >
      {{states.weather.buienradar.attibutes.forecast}}

btw, the weather integration is then created, and without any forecast…

Schermafbeelding 2021-03-12 om 14.10.35
Schermafbeelding 2021-03-12 om 14.10.351692×304 31.7 KB

using:

    forecast_template: '{{states.weather.buienradar.attributes.forecast}}'

doesn’t help, the integration isn’t created in that case
thanks for having a look

2

well, that’s odd. It is the weather integration for Buienradar causing the issue. All other integrations I use (Dark sky, Openweathermap and Weatherbit) do work and make the template weather integration build correctly.
And all 3 template variants work correctly, so I am back to using:

  - platform: template
    name: Composite
    condition_template: >
      {{states('sensor.br_condition')}}
    temperature_template: >
      {{states('sensor.weatherbit_apparent_temperature')|float}}
    humidity_template: >
      {{states('sensor.weatherbit_humidity')|float}}
    forecast_template: >
      {{state_attr('weather.dark_sky','forecast')}}
    pressure_template: >
      {{states('sensor.luftdaten_37248_pressure')|float}}
    wind_speed_template: >
      {{states('sensor.openweathermap_wind_speed')|float}}

Maybe Buienradar has a few days of forecast too little?
issue: https://github.com/home-assistant/core/issues/47805
Guess the output format is different from what is expected, see screenshot in issue