Break up websocket 2 (#17028)

* Break up websocket 2

* Lint+Test

* Lintttt

* Rename

homeassistant/components/websocket_api/error.py

@@ -0,0 +1,8 @@
+"""WebSocket API related errors."""
+from homeassistant.exceptions import HomeAssistantError
+
+
+class Disconnect(HomeAssistantError):
+    """Disconnect the current session."""
+
+    pass