Add required changes to support MQTT discovery that I previously missed. See #6481.

homeassistant/components/light/mqtt_template.py

@@ -66,6 +66,9 @@ PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
 @asyncio.coroutine
 def async_setup_platform(hass, config, async_add_devices, discovery_info=None):
     """Setup a MQTT Template light."""
+    if discovery_info is not None:
+        config = PLATFORM_SCHEMA(discovery_info)
+
     async_add_devices([MqttTemplate(
         hass,
         config.get(CONF_NAME),