Logging message used to list sessions fails with template error (#1132)

Author: vindex10

jupyter_server/serverapp.py

@@ -683,7 +683,7 @@ def start(self):
                 url = serverinfo["url"]
                 if serverinfo.get("token"):
                     url = url + "?token=%s" % serverinfo["token"]
-                info(url, "::", serverinfo["root_dir"])
+                info("%s :: %s", url, serverinfo["root_dir"])
 
 
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