Note that 

value = unicode(value).encode("utf-8")

will also work if value is already Unicode, so a backwards compatible
fix would be to allow passing in:

 * ASCII encoded strings
 * Unicode objects

for the meta data keyword parameters and then apply unicode() to all the
meta-data arguments.

I don't think that we should support non-ASCII encodings for meta-data 
strings passed to setup().

If setuptools is broken in this respect, it needs to be fixed. Dito for
other 3rd party tools.