Comment 4 for bug 449734

http://bugs.python.org/issue7064

is why this change was made.

Reading that, it was done because setuptools assumes that the method
is always called with the full dotted name, when it was just being called
with the last part of it.

However, update-manager isn't using a dotted module path anyway, it's
passing a path.

http://docs.python.org/distutils/setupscript.html#extension-names-and-packages

shows that you would be expected to use

      ext_modules=[Extension('UpdateManager.fdsend',
                             ['UpdateManager/fdsend/fdsend.c'])],

(note . not / in the first line)

Does this in fact work?

Bringing this issue to the attention of the developers on the above
bug might be a good idea (I don't have credentials).

Thanks,

James