Shortcut User-agent computation, as 2to3 won't

update urllib2.__version__ correctly.

--HG--
branch : distribute
extra : rebase_source : 9035aa6fb13225181f7ce22429efa91c771247a6

setuptools/package_index.py

@@ -143,7 +143,7 @@ def find_external_links(url, page):
                 yield urlparse.urljoin(url, htmldecode(match.group(1)))
 
 user_agent = "Python-urllib/%s distribute/%s" % (
-    urllib2.__version__, require('distribute')[0].version
+    sys.version[:3], require('distribute')[0].version
 )