easy_install.py: Upload index only if http status code is 2xx.

src/zc/buildout/easy_install.py

@@ -216,7 +216,8 @@ class AllowHostsPackageIndex(setuptools.package_index.PackageIndex):
             if nc.get('upload-cache-url') \
                 and nc.get('upload-dir-url') \
                 and '==' in requirement \
-                and getattr(f, 'code', None) != 404:
+                and str(getattr(f, 'code', None)).startswith('2'):
+                # http status code is 2xx
                 upload_index_network_cached(
                     nc.get('upload-dir-url'),
                     nc.get('upload-cache-url'),