[Distutils] Making commands extensible by default

[David Cournapeau]

Toshio Kuratomi wrote:
> They don't have bearing on talking about
> redesigning how to design a new architecture that's easy to extend.
>   

Those examples show why extending distutils commands with subclassing +
post processing is not always enough. I don't understand why they would
not be relevant for the design to improve distutils extensibility. They
are quite typical of the usual problems I have when I need to extend
distutils myself.

David