considering that superagent mimics req behavior it is reasonable to have...

... on close instead of on end

I am using Package to install components. And I use my custom installer that takes callback. I am taking callback package.on('end') and I have a bug where files are not uploaded yet and the package is done.
I believe that it's caused because supergent's end is too early. Before the data actually piped into file.
on close event is better here. At least it fixes my bug.