[web2py] Versioning static files or other options for browser cache reloading

[Yarin]

I'm trying to apply a version number to my CSS files as a way to force 
browsers to load the latest version, but the following examples never get 
outputted even though they create valid URLs:

response.files.append(URL('static','css/main.css', vars=dict(v='1208301')))
or
response.files.append(URL('static','css/main.css?v=1208301'))

Why won't these work? Is there a better web2py-way for forcing browser 
cached files to reload?

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