[Distutils] distutils post processing

[Eric S. Johansson]

I'm trying to extend distutiles to do things like fix permissions etc. 
  have a draft that works but I'm  not sure how to invoke it.  I'm 
running it after setup() but as you would expect it always run on any 
setup operation.  How can I limit when my code run only when it's a 
build command?

I tried following the distutiles extension instructions but it is a bit 
thin.  some pointers would be appreciated.  Thanks for your time.

---eric