[Distutils] setuptools: bug in run_script

[Ian Bicking]

Ben Bangert encountered a problem where
pkg_resources.WorkingSet.run_script didn't work; from line 407:

        self.require(requires)[0].run_script(script_name, ns)

If all the packages are already loaded for some reason, then
self.require() returns [].

I don't really understand how we got in this state -- that apparently
packages are available before they are being required.  But so it is; it
might be from a script wrapper created with 0.6a2?