Sometimes (especially when one only starts working with tox, plays with the configuration etc.) it's really crucial to see command outputs live (by commands I mean mostly pip). This patch introduces this feature. It's especially handy when "pip install ..." takes ages to complete and one wants to know why.
The implementation is quick and dirty, I don't know the codebase well enough and that was the easiest way I saw, feel free to reimplement it :)
i agree the option makes sense. The hack is probably ok but i won't merge it without a test -- Which is the hard part here arguably :)
And i won't get to that myself at the moment i think. Adding tests is not as easy currently as it should be :/