fixup: Format Python code with Black

GUI.py

@@ -3,7 +3,8 @@ from pathlib import Path
 
 # Used "tomlkit" instead of "toml" because it doesn't change formatting on "dump"
 import tomlkit
-from flask import Flask, redirect, render_template, request, send_from_directory, url_for
+from flask import (Flask, redirect, render_template, request,
+                   send_from_directory, url_for)
 
 import utils.gui_utils as gui