Device automation config error message improvements (#44656)

Refs #44654, #44655

homeassistant/components/sensor/device_trigger.py

@@ -168,7 +168,10 @@ async def async_get_trigger_capabilities(hass, config):
     )
 
     if not state or not unit_of_measurement:
-        raise InvalidDeviceAutomationConfig
+        raise InvalidDeviceAutomationConfig(
+            "No state or unit of measurement found for "
+            f"trigger entity {config[CONF_ENTITY_ID]}"
+        )
 
     return {
         "extra_fields": vol.Schema(