Fix setuptools handling in Python packages.

- add setuptools dependencies to packages that need it.
- remove setuptools from packages that do not need it.

var/spack/repos/builtin/packages/py-joblib/package.py

@@ -35,6 +35,5 @@ class PyJoblib(PythonPackage):
     version('0.10.2', 'ebb42af4342c2445b175f86bd478d869')
     version('0.10.0', '61e40322c4fed5c22905f67d7d1aa557')
 
-    depends_on('py-setuptools', type='build')
     # for testing
     # depends_on('py-nose', type=('build', 'run'))