[Distutils] warning about old files when installing a package

[Anthony Baxter]

I was recently hunting down a bug that ended up being caused
by a change in packaging, like so:

Before:
        nevow/
              formless.py

After:
        nevow/
        formless/

I upgraded with a 'setup.py install' - this installed the new
code, but didn't remove the old module. This caused brokenness,
because inside nevow, 'import formless' got the old code.
I don't think we want to be destroying files that are also in
the newly-installed package's directory, but I _do_ think we
should at least warn about them. If this seems like a good
idea, I'll whip up a patch. Any other opinions?


-- 
Anthony Baxter     <anthony at interlink.com.au>
It's never too late to have a happy childhood.