Abort if the instance folder cannot be created

According to the comment, the instance folder should exist in any case.
But a PermissionError was ignored silently.

Since Python 3.9 is the minimum required version, it is safe to use
"exist_ok" added in Python 3.2 and avoid exception handling.

docs/tutorial/factory.rst

@@ -56,10 +56,7 @@ directory should be treated as a package.
             app.config.from_mapping(test_config)
 
         # ensure the instance folder exists
-        try:
+        os.makedirs(app.instance_path, exist_ok=True)
-            os.makedirs(app.instance_path)
-        except OSError:
-            pass
 
         # a simple page that says hello
         @app.route('/hello')

examples/tutorial/flaskr/__init__.py

@@ -21,10 +21,7 @@ def create_app(test_config=None):
         app.config.update(test_config)
 
     # ensure the instance folder exists
-    try:
+    os.makedirs(app.instance_path, exist_ok=True)
-        os.makedirs(app.instance_path)
-    except OSError:
-        pass
 
     @app.route("/hello")
     def hello():