[Distutils] distlib and wheel metadata

[Vinay Sajip]

> Managing backwards compatibility is probably the single most important thing we can do here. 
> There are almost 800,000 files on PyPI that someone can download and install, telling all 
> of them they need to switch to some new system or things are going to break for them is 
> simply not tenable. 

I agree. But if packaging is going at some point to break out of allowing completely bespoke 
code to run at installation time (i.e. executable code like a free-for-all setup.py, vs. 
something declarative and thus more restrictive) then IMO you have to sacrifice 100% backwards 

compatibility. See my comment in my other post about the ability to install old releases - 
I made that a goal of my experiments with the parallel metadata, to not require anything other 
than a declarative setup() in order to be able to install stuff using just the metadata, so that 
nobody has to switch anything in a big-bang style, but could transition over to a newer system 
at their leisure. 

Regards, 

Vinay Sajip