From a0f4bf4bb60a95a959314f3540a42f186f1f8ace Mon Sep 17 00:00:00 2001
From: TheGreatAlgo <37487508+TheGreatAlgo@users.noreply.github.com>
Date: Fri, 7 Jul 2023 23:29:13 +0200
Subject: [PATCH] fix: improve error message

---
 src/werkzeug/routing/rules.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/werkzeug/routing/rules.py b/src/werkzeug/routing/rules.py
index 63e62c941..d65dce028 100644
--- a/src/werkzeug/routing/rules.py
+++ b/src/werkzeug/routing/rules.py
@@ -454,7 +454,7 @@ def __init__(
         websocket: bool = False,
     ) -> None:
         if not string.startswith("/"):
-            raise ValueError("urls must start with a leading slash")
+            raise ValueError("urls must start with a leading slash:", string)
         self.rule = string
         self.is_leaf = not string.endswith("/")
         self.is_branch = string.endswith("/")