Deprecate Python 3.6 support, 3.8.0 is out (#27680)

homeassistant/bootstrap.py

@@ -93,6 +93,17 @@ async def async_from_config_dict(
     stop = time()
     _LOGGER.info("Home Assistant initialized in %.2fs", stop - start)
 
+    if sys.version_info[:3] < (3, 7, 0):
+        msg = (
+            "Python 3.6 support is deprecated and will "
+            "be removed in the first release after December 15, 2019. Please "
+            "upgrade Python to 3.7.0 or higher."
+        )
+        _LOGGER.warning(msg)
+        hass.components.persistent_notification.async_create(
+            msg, "Python version", "python_version"
+        )
+
     return hass