Added the "/.errors" route to the application in the "create_test_app" function in testlib.py, to make it easier to test.

tests/testlib.py

@@ -40,6 +40,11 @@ def create_test_app() -> Flask:
         """The test view to return the CSRF token."""
         return render_template_string("{{csrf_token()}}")
 
+    @app.get("/.errors")
+    def get_errors_view() -> str:
+        """The test view to return the CSRF token."""
+        return render_template_string("{{get_flashed_messages()|tojson}}")
+
     return app