Is it better to use a comma as? after try-exception?

Usually from exception

try:
    pass
except Exception, exception:
    pass

try:
    pass
except Exception as exception:
    pass

They use it in these two ways. Which one is the standard?

The second source code is okay to run at 2.6, but in 2.5, it's called invalid, so I'm thinking about what to use.