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-csvkit/package.py

@@ -34,6 +34,7 @@ class PyCsvkit(PythonPackage):
 
     version('0.9.1', '48d78920019d18846933ee969502fff6')
 
+    depends_on('py-setuptools', type='build')
     depends_on('py-dateutil', type=('build', 'run'))
     depends_on('py-dbf', type=('build', 'run'))
     depends_on('py-xlrd', type=('build', 'run'))