<console> can't distinguish stdout with stderr

[adam-a-smith]

I use <console> to indicate output from a program. But programs have 2 channels for output: stdout and stderr. Having both of them in mixed output would be good.

For example, something like this:
<console>
    <output>Now calculating...</output>
    <error>Exception in thread "main" java.lang.RuntimeException</error>
</console>

And then <output> and <error> would be styled differently (e.g. <error> making red text).