[Zope] retry <> '' ??

[Florian Lindner]

Hello,
if I try to access a object without sufficient permissions cookie 
crumbler redirects me to my login page with these parameters:

http://[...]/login.zpt?came_from=http%3A//[...]/secret.zpt&retry=&disable_cookie_login__=1

If I enter a wrong password retry is iterated:

http://[...]/login.zpt?came_from=http%3A//[...]/secret.zpt&retry=1&disable_cookie_login__=1
http://[...]/login.zpt?came_from=http%3A//[...]/secret.zpt&retry=2&disable_cookie_login__=1
...

I want to render a HTML-Code only if retry has a value. Sounds easy, but 
somehow I didn't get.
I tried:
<p tal:condition="python: request.retry<>''">
<p tal:condition="exists: request/retry">
<p tal:condition="request.retry">

But none of these works as I want to.

Thanks,
Florian