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-restview/package.py

@@ -33,6 +33,7 @@ class PyRestview(PythonPackage):
 
     version('2.6.1', 'ac8b70e15b8f1732d1733d674813666b')
 
+    depends_on('py-setuptools', type='build')
     depends_on('python@2.7.0:2.7.999,3.3:3.5')
     depends_on('py-docutils@0.13.1:', type=('build', 'run'))
     depends_on('py-readme-renderer', type=('build', 'run'))