[Distutils] patch: ez_setup.py: separate default version and minimum version of setuptools

[zooko]

>> Agreed.  So in order to automatically satisfy our dependency on
>> simplejson using simplejson's source tarballs, we can either ask Bob
>> Ippolito (the author and packager of simplejson) to please switch to
>> the patched version of ez_setup.py and pass min_version="0.6a9" to
>> it, or else we can ask him to please set his version="0.6a9" and
>> start hosting setuptools 0.6a9 eggs for his users.

...

> So bear in mind that since it's already *possible* to do this, it's  
> unlikely I'll accept a patch that makes it *easy* for people to  
> keep using outdated alphas.  :)

Oh yes, we too prefer for our users to use newer versions of  
setuptools.  I sympathize with your motivation.  :-)

Actually I think this patch makes it easier in some cases for people  
to gracefully upgrade to newer versions of setuptools.

Consider our case: we are required to service users of Ubuntu dapper  
and to do so without requiring them to first upgrade their version of  
setuptools.  If we use standard ez_setup.py, then what happens is  
that all of our users (not just the Ubuntu dapper using ones) get  
setuptools v0.6a9 installed.  Eventually, our users will upgrade from  
Ubuntu dapper to a newer Ubuntu, and they will upgrade their version  
of setuptools when they upgrade their operating system, but our other  
users -- the ones whose version of setuptools is automatically  
installed by our ez_setup.py script -- will be stuck with v0.6a9.

So in order to support our dapper users while also installing a newer  
version of setuptools for non-dapper-users, we patched our  
ez_setup.py.  Now dapper users proceed as normal, but all our other  
users get setuptools v0.6c7 installed.

This is already good enough for us -- we don't mind maintaining a  
slightly different version of ez_setup.py than the official one.  The  
reason why this patch going into the official ez_setup.py would help  
us is that if packages like simplejson used it (and allowed a  
sufficiently old version of setuptools) then we could add simplejson  
to the list of dependencies that are automatically satisfied by  
setuptools even while satisfying the above-mentioned policies.

By the way, I'm separately submitting a patch which, if it can be  
made to work, might allow us to automatically upgrade people to newer  
versions of setuptools when they follow our installation procedure.

Regards,

Zooko