hint: when passing around test output, consider using subunit

[Ian Clatworthy]

Robert Collins wrote:
> I just thought I'd mention this. As you may or may not know, bzr has
> subunit support.
> 
> When giving test logs to other devs, using subunit output is a great way
> to make it easy to introspect the logs:
> 
> bzr selftest --subunit > tests.log
> subunit-ls < tests.log
> subunit-filter --no-skips < tests.log | subunit2pyunit
> 
> and more :)

Is this worth updating the testing section of the Developer Guide with this?

Ian C.